Aperture, or peep, sights are useful tools for accurate rifle shooting without a scope. It is the iron sight system capable of the highest level of accuracy. The "peep" is the rear sight, with a small hole through it. The front sight is normally a blade, post or bead. The rear sight is held close to the eye, and the shooter aims by placing the front sight within the narrow field of view allowed by the small peep hole.
Drill and tap a hole for the swivel stud bolt. The bolt has a small hole through the side. This hole will serve as the peep. The hole for the stud should be located on top of the gun, at the centre of the gun's width. It should be rearward enough that the stud will be near your eye when you raise the gun to your shoulder. Be sure to not drill too deep into your firearm, or you may damage the inner parts.
Install the swivel stud bolt in the top of the rifle. Screw the bolt into the pre-tapped hole. Be sure the peep opening on the top of the bolt is pointed in the same direction as the barrel.
Measure the height from the centre of the peep hole to the firing pin. Use the ruler to determine how high the peep is. If it is too high, turn the bolt one half turn. This will keep the peep pointed in the right direction, but will bed the bolt deeper (and lower) into your firearm.
Measure the desired height of your front sight. Use the ruler to measure from the centre of the barrel's bore to the same height as your peep. You want your front sight to be the same height as the centre of your peep hole to ensure the sight is accurate. The centre of the bore will be level with the firing pin, so you can determine how high your front sight should be above the barrel.
Solder the front sight onto the barrel, near the muzzle. Be sure the height of the sight places it in the centre of the peep when the rifle is on target. Also, be sure the front sight is in the middle of the barrel. Otherwise, the sights will not align at all.
Allow your barrel to cool before firing it. Once the soldering and the barrel metal has cooled, you can test fire your rifle. Adjust the peep for distance by turning it one half turn into or out of the rifle stock.
If you do not have a front blade sight, you can use a bolt without a head, drilled into your barrel.
Always be sure to unload your firearm before repairing, modifying or cleaning. Also follow all universal gun-safety rules. Use caution when drilling into your firearm. Do not drill or insert a bolt where it will interfere with the firing mechanism or the bore.