Hello folks, many times I have needed to hand tap holes in the field and it is sometimes difficult to maintain the tap square to the hole. One method that will help with this, is to have a piece of keystock or other square material with a hole in it that is the same size as the OD. of the tap. Place this piece flat against the material that you are tapping and line-up the through hole with the tap size hole and proceed to start the tap, once you have cut a few threads you can remove the block or continue to run the tap on through the material or to the appropriate depth. The thickness of the block should roughly equal the length of the threads on the tap. I have found this method to be a great help in keeping the tap square to the material while tapping. Hope it helps some of you. Regards, aevald