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Under One Roof

Canadian Roofing Reference Manual

2.4.5 Bolts

The following bolts are available in a variety of sizes, materials, coatings, and thread types:

  • Carriage bolts have coarse threads. The head variations include countersunk flat-topped head in addition to round head. Shoulder keeps the bolt from turning when the nut is tightened. They are used for wood and metal, heavy construction.
  • Machine bolts are made in both square and hex head forms and have either square or hex nuts. These bolts are available with coarse and fine thread. They are used in general construction, wood and metal.
  • Stove bolts are made with slotted round, flat or oval heads and have coarse threads. These bolts are usually smaller than carriage bolts.
  • Masonry bolts and anchors are made in many forms. They all work according to the same principle; as the bolt is tightened, the shell around it expands and grips the inside of the hole.
  • Toggle bolts are used for fastening to hollow walls. Holes large enough to pass the spring-loaded wings must be drilled in the wall. The wings spread out and bear against the wall as the head is screwed.
  • Molly bolt is similar to a toggle bolt and is also used for attaching to hollow surfaces. The bolt is passed through a clearance hole and as the head is turned, the legs are pushed outward to grip the wall.
  • Turnbuckle consists of a steel sleeve and two screw eyes. Half of the sleeve and one screw eye have right-handed thread, the other half is a left-hand thread. Turning sleeve left or right moves the screws eyes in or out.
  • U-bolts, J-bolts and eye bolts are all special-purpose fasteners and holders, produced in various shapes.