Drawboring uses slightly offset peg holes to force a mortice and tenon joint tighter together. First you bore a hole through the cheeks of the mortice, without the tenon in place. You then insert the tenon and mark the position of the hole on the tenon. You then pull the joint apart again and bore through the tenon, offsetting the hole toward the shoulder of the tenon. When you reassemble the joint and drive a tapered peg through the offset holes, the tenon will be forced deeper into the mortice.