 A jig can be a stationary device that the wooden pieces are clamped into, or a portable device that is clamped onto the wooden pieces.When joining boards at a right angle, it is important that the cuts are precise and square to prevent gaps or un-perpendicular joints between the boards.Some woodworkers lay out their project before drilling their pocket holes and mark the face of the board that they want to drill to ensure the hole is in the correct location.