Machine screws are used in fastening nearly all types of hard materials. Commonly used with flat or lockwashers. Especially useful in metal-to-metal or where heavy duty fastening is required..
Extension springs are wire coils designed to become longer under load..Their turns are normally touching in the unloaded position, and they have a hook, loop or some other means of attachment at each end.
A lag screw is similar to a wood screw, but generally is much larger with a hexagonal head..Lag bolts are designed for securely fastening heavy timbers to one another, or to fasten wood to masonry or concrete.
Sheet Metal Screw, #8 x 1-1/4 in, 18-8 Stainless Steel Truss Head Phillips Drive, 18 PK.They provide secure metal-to-metal and metal-to-wood fastending.