Simple Sleeve for Sparrows practise lock cylinders

A quick sleeve I designed for holding Sparrows training lock cylinders, too awkward to hold directly in your hand and I found that the gap in the front of the keyway caused trouble when I clamped them in my vice (nowhere for the pick to rest when trying to get at pin 1).

You can remove the cylinder by sticking a key in and turning 90 degrees, but if you don't have a key there's a 4mm hole in the back you can use to poke the cylinder out.