A little to the right of leg, and one inch from the lower edge of the fixed upright, cut a slot two inches high and one inch wide; make a corresponding hole in the loose upright.
Fig 8
Take a strip of board two feet long, two inches wide, and one inch thick. On a line drawn lengthwise through the middle measure one inch from end and mark; then two inches from that point on same line make a second mark; at both those points bore holes with half-inch bit and fit in a peg at each hole. The pegs will be one and one half inches apart.
Then at intervals of one inch bore two alternate rows of holes with half-inch bit, as far as the length of the strip allows. Run this strip through the slot in loose board as in [fig 8], and through the corresponding slot in upright put a peg in a in front of loose board and a peg in b behind loose board; these pegs will hold the strip firm in the slot in the loose board.
According to the size of the object to be held in use, draw the loose board toward you and put third peg into hole at proper distance to keep the loose board parallel with the fixed upright.
You see by having holes enough in the strip you can adjust the vise to any size. Of course you understand that this is not needed in small work.
If you look closely at [fig 6] you will find that there is still one thing unexplained: the rows of holes in the front board.