In woodworking and fabricating, a leg vise can be enormously useful. They offer a large, flat clamping surface on which you can impart a surprising amount of clamping force. A properly aligned leg vise can hold large workpieces such as doors or 6x6 beams. But few companies make proper woodworking leg vises or even the hardware for them. The issue with making a leg vise is keeping the chop (the part that moves) parallel to the bench leg when under tension. This Instructable features a solution.
I make all my leg vises at TechShop