Having a sling on your firearm brings advantages, including being able to carry it over your shoulder, freeing up your hands for other tasks. Many shotguns, epically double-barrel models, do not come equipped with factory installed swivel-studs for attaching a sling. Adding sling swivel-studs on a over-under shotgun is not a complicated process, but there are a few details that you must pay attention to. Most critical is that you do not try to install the rear stud too close to the butt end of the gun, or the wood can split and ruin the stock.
Open the vice wide enough to accommodate the shotgun stock. Fold the towel in half, the long way, and lay it across the jaws. Insert the shotgun stock, upside-down, halfway into the vice with the towel padding the gun. Close the vice just enough to hold the stock in place.
Cover the ridge along the bottom (that is now facing upward) of the butt of the stock with masking tape. Measure in a minimum of 2 inches from the butt end of the stock with the tape measure and mark with the pen. Be sure to measure from the wood, not the recoil pad.
Attach the drilling guide to the stock, aligning the guide hole in drilling guide in the centre of the stock ridge and with the pen mark on the masking tape.
Attach the drill bit to the drill. Insert the drill into the drill guide and drill the hole in the stock. Remove the drill guide and the masking tape.
Twist the swivel-stud threads into the hole as far as possible with your fingers. Insert the Phillips-head screwdriver into the hole in the stud. Using the screwdriver for leverage, finish twisting the stud, a half-turn at a time, until the head is seated against the wood.
Open the clamp-on swivel-stud with the hex head screwdriver and place it around the barrel, approximately 1 inch in front the forearm (front) of the stock.
Apply a drop of thread sealer to the clamp-on swivel-stud's screw and tighten in place.
Use the metric (centimetre) side of the tape measure to be sure the rear swivel-stud goes in straight by measuring the distance between the stud's head and the wood, on all sides, every few turns.
Do not drill less than 2 inches from the butt end of the stock as it may cause the wood to crack or split.