Bolts and Screws

Lag Screw. Referred to interchangeably as a lag screw or a lag bolt (lag bolt is perhaps a more precise name), this fastener has a tapered shaft, with coarse threads that run about half its length. Lag bolt heads are hexagonal or square.

The lag bolt is essentially a longer and stronger version of the ordinary wood screw, though its head is driven using a wrench or socket. One common household use is in deck construction. Typically, lag bolts can be purchased in three-inch to six-inch lengths, though longer lags of up to a foot or more in length are to be found.

Stove Bolt. At one time, the name stove bolt distinguished bolts with coarse threads (machine bolts typically having finer threading). However, the term as used today generally means a bolt intended for use with a nut (as distinct from a machine screw or bolt). The entire length of a stove bolt's shank is threaded. Stove bolts are usually- found in lengths ranging from three-eighths of an inch to four inches, in diameters from about an eighth to three-eighths inch

Carriage Bolt. Carriage bolts most often have rounded heads, with a shaped shaft immediately beneath the head. Usually the shape is square (though finned and ribbed varieties are also sold). Whatever its shape, the shaft neck is set into an opening in the workpiece, and prevents the bolt from turning as the nut is tightened or loosened. Typically, only a third to a half of the bolt's length is threaded. 

Carriage bolts are sold in a wide variety of lengths, from an inch or less to twenty inches or more, in diameters from about three-sixteenths to three-quarters of an inch. Flat washers are generally used between the nuts and wood surfaces Machine Bolt. These are rodlike threaded bolts with wrench heads that are square or hexagonal in shape. When used with a nut, two wrenches are required to tighten the machine bolt. 

Washers and nuts. Flat disks called washers are used to prevent the marring of the material being fastened, to help secure the bolt or nut, or to cover a hole that is larger than the head of the screw or bolt. Nuts, like screws, come in a vast array of shapes and sizes, in cluding those with hexagonal, square, wing, and acorn (or cap-head) shapes, with a flange attached (flanged nuts look as if a washer is an 233 integral part of the nut), and other varieties as well. 

Hangers, wall fasteners, and anchors. As many types of screws and bolts as there are, there are even more hangers, anchors, and fasteners. There are molly bolts and toggle bolts; screw eyes and shoulder hooks; lead, hollow-wall, nylon, and plastic anchors; and a considerable number of other options.