The corners are assembled with mortise and tenon. It is attached with mortise and tenon joints and strengthened with oak pegs. The tenon is cut to fit the mortise hole exactly. Mortise and tenon joints are attested from the earliest Predynastic period. There are no mortise and tenon fastenings, and no sewing. One of the most important indigenous woodworking techniques was the fixed mortise and tenon joint. In its most basic form, a mortise and tenon joint is both simple and strong. To prevent the columns from twisting or slipping, a mortise and tenon was used. Whichever design is used, wooden timbers should have square ends without mortise and tenons. Older mortise locks may have used warded lock mechanisms. The mortise locks used at Monticello were warded locks. Pin tumbler locks are still the most common kind of mortise lock used today. Other trenails are tapered with the large end being longer than the mortise. The next major innovation to mortise lock mechanisms came in 1865. To create the mortise for the biscuit, a biscuit joiner is usually required.