Hi chain gang, one more variant: the Rohloff Caliber 2. (Same Rohloff who make the 14 sp. Speedhub, btw.) Very popular in German workshops and very similar to the Belgian tool on eBay. It´s always one of the first special bike tools I show my cycle maintenance class students, not only because it´s so useful, but also because it´s so hard to guess and at the same time it´s so simple to use once you know how.
You hook the concave bit protruding out of the main body into the chain, then try to push the convex bit on the other end in between the sideplates. If the main body of the tool stays at an angle, the chain is ok. The closer the main body gets to the chain, the more worn the chain is, and when the main body touches the chain with both the concave and the convex bit completely vanishing between the sideplates, the chain is worn amd must be replaced.
One side of the tool is for steel chainrings, which allow for a little bit more chain wear, the other for alloy chainwheels which need closer tolerances, i.e. the chain wears quicker.
I do hope I´m not stating the obvious, but maybe some of the non-shopowner listmembers will in future be able to save valuable Regina threaded blocks (on-topic contents!) which, after all, must now be treated with extra care as they´re not being made any more.
Toni Theilmeier, Belm, Germany, who works at a state comprehensive and so is used to stating, re-stating and re-re-stating the very obvious.