The slot is to be used once. The first time the plug is installed into one's rifle, it won't go. A 'tool' is inserted into the slot, and the plug is torqued into the rifle using the tool. This forces the thin rim on the end of the plug into the barrel. This makes for a seal against blow by, around the end of the plug. One could use a pipe wrench.

If every thing is right, the marriage of plug and barrel is perfect, and blow by is zero. After the slot is utilized the one time, it no longer has a purpose. The second time the plug is installed in the rifle it is done with fingers; fingers only. The nth time the plug is installed, and removed it is done with fingers only. It is kinda amazing to do a long long session at the range, and then just unscrew the plug with fingers, and observe no soot on the threads.

No teflon tape, nor anti-seize grease is required, if one uses Blackhorn powder. Cannot speak about using other powders. The plug never ever sticks; just simply, easily unscrews. Me, i put one drop of oil on the threads, before the plug is installed into the rifle.

However, the rim on the end of the plug is quite fragile; one never ever wants to drop the plug; this ruins the seal. If the rim is just bent, it may be able to be fixed. If the rim is dinged, the plug will thereafter always leak.

It isn't hard for me to use a socket, and a ratchet to install, and remove breech plugs, so i am unable to understand why some are so enamored, with these plugs that can be installed, and removed, with only fingers.