A carpenter's vise holds a piece of wood securely in one place while the woodworker shapes it. Without a vise of some kind, wood can slip while the carpenter is using a sharp tool, causing the project to be ruined at best or the carpenter to be injured at worst. Commercially made carpenter's vises are usually metal with a rotating screw to open and close them. They are fairly expensive; however, a cheap and effective vise can be made using scrap lumber and some screws.
Cut an 18-inch long section of 1-by-8-inch lumber. This will be the base of the carpenter's vise. It can be permanently attached to a workbench with screws if desired.
Cut a length of 2-by-4-inch lumber the same length as the base is wide. This will be 7 1/4 inches for most commercially milled lumber, which is smaller than the stated dimensions. Screw the 2-by-4-by-7 1/4-inch block crosswise a couple of inches from the end of the base, where it will act as an end block.
Cut a length of 2-by-8-inch lumber the same length as the end block in step 2--usually 7 1/4 inches. This block will be cut in two pieces to act as the fixed wedge and the movable wedge.
Set the blade of a table saw with a tapering jig to 40 degrees so that it will make a beveling cut. Set the jig to 15 degrees so that it will cut the wood block at an angle, to make two complementary wedges. This cut is called a compound rip bevel.
Cut the 2-by-8-inch block along the wood grain using these saw settings to make two roughly equal beveled wedges. If one wedge is a little larger than the other, that's fine.
Rejoin the two wedges and position them on the base so that the cut is oriented across the width of the base, not along its length, and the wedge closest to the end block slides under the other piece on its bevel, not over. Leave a gap between the end block and the innermost of the two complementary wedges that is the size of the narrowest piece of wood that you will want to grip with the finished vise. Screw the outermost wedge to the base in this position. This is the fixed wedge.
Place a piece of wood that you wish to clamp in place against the end block of the vise. There will be a gap between the piece of wood and the fixed wedge. Slide the narrow end of the movable wedge into this gap until it won't go any further and tap it with a mallet to clamp the piece of wood firmly into position.
Use good quality wood to construct your vise, since it will be under a fair amount of pressure when in use.
Power tools are dangerous and may cause injury. Follow good safety procedures when using saws and drills.