Many times some on this forum have asked how to drill a hole from the barrel tang through the stock and keep it square. These 2 little dowels are what I use to drill holes and keep the holes square to the surface.
All you need is a dowel that is square on both ends with a hole drilled through the middle that is square. You can make these out of an old shovel handle or any other old dowel. They can be a block of square wood but the hole needs to be perfectly straight. This is best done on a lathe or a drill press. If you don't have them a piece of angle iron that has been cut off square will work for a drill guide to drill the hole in a wooden block. Just hold the angle iron endwise on the block and keep the drill bit in the corner of the angle iron while you drill the hole. That will give you a straight hole.
When using these I first use a ice pick to make a deep impression where the hole is to be. That will keep the drill in position when beginning. Place the drill bit through the hole in the dowel or block and position the bit where the hole is to be drilled. Now slide the dowel down onto the surface and hold it flat on the surface firmly while you drill the hole. If done correctly you will have a perfectly square hole and the head of the screw will fit properly in the countersink. Works great on patchbox holes and all others for keeping the screw heads square.
Notice that one of my blocks has two small screws in the end. I use these two screws to square up the dowel guide on a surface that is curved in one direction such as on a tang of a rifle. The two screws can be adjusted to make the dowel guide square on the curved surface. Hope I have made this clear. No charge.