Fasteners come in many different forms. To make it easy for you, we’ve compiled the data below as a guide for figuring out what each fastener is called. Scroll down to learn about many different types of nuts, bolts and screws!*
*Note: Bolts are fasteners that require a nut or pre-tapped hole to be installed. Screws use their threads to provide their own holding power. The terms in the industry are commonly mixed so sometimes you will see something that is called a screw or a bolt that is actually the opposite. Example: Lag Bolts and Lag Screws are the same thing. We have broken them down according to their true definition.
Select a category below to view a picture and information on that type of fastener.
Types of Bolts
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Carriage BoltsAlso known as a “coach” bolt, has a domed or countersunk head. The square section under the head grips into the part being fastened preventing the bolt from turning when the nut is tightened. |
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Hex Head BoltsHex tap bolts, hex cap screws, trim head hex cap screws, and hex serrated flange bolts fall under this category. They share a hexagonal head and are driven with a wrench. Referred to as both bolts and screws. |
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Shoulder BoltsShoulder bolts (also known as shoulder screws or stripper bolts) are machine screws with a shoulder between the thread of the screw and the head of the part. Once installed, the non-threaded portion extends out of the surface of the application site, allowing the bolts to act as dowels or shafts for moving parts. They can be installed by hand or with a socket (Allen) driver. |
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Socket Cap ScrewsSocket cap screws are available in button socket, button flange socket head, flat socket, and socket cap. Driven with a socket wrench or a hex Allen key. The term socket head cap screw typically refers to a type of threaded fastener whose head diameter is nominally 1.5 times or more than that of the screw shank diameter. |
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Socket Set “Grub” ScrewsSet screws are most often headless (aka blind), meaning that the screw is fully threaded and has no head. A blind set screw, known in UK as a grub screw, is almost always driven with an internal wrenching drive, such as a hex Allen key. Socket set screws are installed in threaded holes or inserts. |
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Square Head BoltsSquare Head Bolts are similar to hex cap screws but with a 4-sided head. This head style allows for a wrench to grip more easily onto the head of the bolt. The head also provides a larger gripping area as compared to a standard 6-sided hexagonal head. |
Types of Screws
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Deck ScrewsOur deck screws feature a type 17 point (notched point at the tip) to aid in chip removal during thread cutting which allows for an easy installation in wood and composite deck materials. A bugle head and square drive help to eliminate the stripping effect sometimes experienced with other types of drives. |
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Hex Lag ScrewsLag screws, also called lag bolts, are large wood screws. The head is external hex and are driven with a wrench. Used for lag together lumber for framing, machinery to wood floors, and other heavy duty applications. |
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Self-Drilling ScrewsSelf-drilling screws have a sheet metal thread with a self-driller cutting (TEK) point to pierce through 20 to 14 gauge metals. The higher the TEK number, the larger the drill point to pierce heavier gauge metals. |
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Sheet Metal ScrewsSheet metal screws (SMS) have sharp cutting threads that cut into sheet metal, plastic or wood. They have a fully threaded shank and sometimes have a notched point at the tip to aid in chip removal during thread cutting. |
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Wood ScrewsWood screws are partially threaded with large cutting threads and a smooth shank. They are designed to slide through the top piece of wood and tightly pull all boards together. |
Types of Nuts
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Cap NutsThe cap nut, also known as the acorn nut, gets its name from its shape. The nut has a domed top to prevent contact with the external thread. |
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Castle NutsUsed with cotter pins to prevent loosening, a castellated nut, also called a castle or slotted nut, is a not with slots cut into the top. Used in low-torque applications such as holding a wheel bearing in place. |
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Coupling NutsA coupling nut is a threaded fastener used for joining two male threads, most commonly threaded rod. The outside of the fastener is a hex so it can be driven with a wrench. |
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Flange Serrated NutsA flange nut is a nut that has a wide flange at one end which acts as an integrated washer that does not move or spin. The serrated flange distributes the pressure of the nut over the part being secured and creates a locking action to prevent loosening. |
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Hex Finish NutsHex finish nuts are used for fastening to a hex cap screw, socket cap screw or bolt. The most common nuts, hex finish nuts are hex shaped with internal threads and driven with a wrench. |
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Hex Jam NutsA jam nut is often used when a nut needs to be locked in place without clamping to another object. Hex jam nuts are hex shaped with internal threads, but they are thinner than hex finish nuts. |
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Heavy Hex NutsLarger, heavier, and thicker than a standard hex nut. Heavy hex nuts are hex shaped, internally threaded, and driven with a wrench. Often used with hex cap screws and carriage bolts. |
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Hex Machine NutsA machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4″ diameter. |
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Hex Machine Nuts Small PatternA machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4″ diameter. |
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Keps-K Lock NutsAlso known as a keps nut, a k-nut or a washer nut, a keps-k lock nut has an attached free spinning lock washer. Keps nuts are designed to make assembly more convenient. |
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Knurled Thumb NutsA knurled head thumb nut or thumb nut has a knurled outside surface rather than a hex, which facilitates tightening by hand. Often used in decorative finishes or applications. |
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Nylon Hex Jam NutsA low-profile lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener. |
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Nylon Insert Lock NutsA nylon insert lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener. |
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Slotted Hex NutsSlotted hex nuts are nuts with portions cut out designed to be used with a cotter ping to create a locking mechanism. These nuts are similar to a castle nut but have a lower profile which sometimes makes them a better option. |
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Square NutsA four-sided nut that may be flat or beveled on top. Square nuts provide a greater surface contact area which provides more resistance to loosening. Typically mated with square head bolts. |
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Structural Heavy Hex NutsStructural hex nuts are comparable to finish nuts but are made to be thicker and much stronger. They are typically used in steel to steel structural connections. |
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T-NutsA t-nut or tee nut is used to fasten wood, particle or composite board leaving a flush surface. A long thin body with a flange at one end resembles a T in profile. T-nuts often have 3 or 4 prongs that sink into the surface providing better retention. |
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Break Away or Shear NutsShear nuts are cone nuts with a hexagonal gripping point. They are designed with an intentional flaw to snap the hexagonal head off once the maximum torque is reached. Leaving behind a protective cone nut that cannot be easily removed. |
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Tri-Groove NutsTri-groove security nuts have a tapered diameter making them difficult to grip with grabbing devices such as adjustable wrenches or pliers. These nuts require a special unconventional gripping device to install them making them more secure than a typical nut. |
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Wing NutsWing nuts are threaded nuts with wings on each side of the body allowing for manual turning and installation. Easy hand assembly and used when the nut needs to be removed often. |
Types of Washers
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Belleville Conical WashersBelleville conical washers are a type of washer that adds extra tension to a fastener assembly. They are commonly used in stacks to increase the load, deflection or both to an assembly depending on the stack. These washers can be considered lock washers because they add tension and absorb vibration to an assembly. |
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Dock WashersDock washers are heavy duty washers, often used to build docks. Also used in heavy duty construction where a thick washer is needed, dock washers are similar to fender washers with a small inside diameter hole. |
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Fender WashersFender washers are round washers with a small inside diameter hole. Fender washers are used to prevent pull-through and provide a greater bearing surface under the fastener. |
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Fender Washers – Extra ThickFender washers are round washers with a small inside diameter hole. Extra thick fender washers are thicker than standard fender washers and are used to prevent pull-through and provide a greater bearing surface under the fastener. |
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Finishing Cup WashersFinishing cup washers form a cup for the head of the screw or fastener to fit in, creating a finish flush with the top of the head. Used for finishing, cup washers are shaped like a cup. |
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Flat WashersFlat washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened. |
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Flat Washers – Extra ThickExtra thick flat washers thicker than standard flat washers. These washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened. |
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Flat Washers – Military StandardMilitary standard (MS) flat washers go through extensive inspection for chemical, physical and dimensional qualities. MS washers must meet specific inner diameter and outer diameter specifications. |
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Flat Washers – 900 SeriesFlat washers in the 900 series are round and thinner than a standard flat washer with a smaller inside and outside diameter. |
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Lock Washers – Split RingSplit ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape. |
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Lock Washers – High CollarHigh collar lock washers are designed to fit under the head of a socket cap screw. Split ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape. |
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Lock Washers – External ToothExternal tooth lock washers are used for locking and tension. Round washers with teeth on the outside, used for maximum holding power. Must be used with fasteners with adequate head diameter. |
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Lock Washers – Internal ToothInternal tooth lock washers are used for locking and tension. A round washer with internal teeth, designed to prevent a nut or screw head from loosening with the strut action created by the teeth. |
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NAS WashersNAS washers are round washers with a smaller inner and outer diameter. Often used in military applications because of the strict measurement specifications. |
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Neoprene EPDM WashersRound washers that are slightly beveled with a neoprene lining. Often used with sharp point and self-drilling TEK screws to make a watertight seal around the screw or metal roofing or siding. |
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Structural WashersStructural washers are thick and strong, built for heavy duty applications such as construction. These washers can be found in steel beams and girder fastener assemblies. |
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Square WashersSquare washers are square in shape and may be flat on both sides or flat on one side and beveled on one side. Often used with square head bolts, square washers prevent pull through and provide a larger surface area and greater hold than standard round flat washers. |
Types of Screws
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Deck ScrewsOur deck screws feature a type 17 point (notched point at the tip) to aid in chip removal during thread cutting which allows for an easy installation in wood and composite deck materials. A bugle head and square drive help to eliminate the stripping effect sometimes experienced with other types of drives. |
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Hex Lag ScrewsLag screws, also called lag bolts, are large wood screws. The head is external hex and are driven with a wrench. Used for lag together lumber for framing, machinery to wood floors, and other heavy duty applications. |
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Self-Drilling ScrewsSelf-drilling screws have a sheet metal thread with a self-driller cutting (TEK) point to pierce through 20 to 14 gauge metals. The higher the TEK number, the larger the drill point to pierce heavier gauge metals. |
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Sheet Metal ScrewsSheet metal screws (SMS) have sharp cutting threads that cut into sheet metal, plastic or wood. They have a fully threaded shank and sometimes have a notched point at the tip to aid in chip removal during thread cutting. |
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Wood ScrewsWood screws are partially threaded with large cutting threads and a smooth shank. They are designed to slide through the top piece of wood and tightly pull all boards together. |