Geissele Automatics Gas Block Roll Pin Tool;

The hole in the tip of the gas block roll pin tool is sized so that the roll pin will need to be pressed into the tool first (the roll pin will not just slide in). stand the roll pin on a hard surface and tap the tool onto the pin to seat it in the tool. When the hole in the gas block grabs the roll pin, the pin will collapse enough so the tool can be removed from the roll pin. Afterwards, all that is needed is a tap with a punch to seat the roll pin in the gas block.