Humane Dispatchers?

Does anyone on here use them? Any tips or advice?

The wall mounted type I have bought has come with no instructions at all!

i have a 'humane dispatcher', excellent bit of kit, cant remember where i got it, might have been on ebay, mine is like a pair of pliers that dont fully close. easy to use, squeeze fully and then stretch neck  a bit and all done, tried to dispatch manually before but found technique difficult and head came off, much less frantic with the dispatcher