I think they'll be useful in awkward areas Glenn. I'll be using one on the seat of the RCAF Starfighter, so we'll see what they turn out like.
Jim, do you mean the 'Expo' tool, or the 'rubber' hoses ?!!
If it's the tool you're asking about, it's a little jig to clamp micro tubing, such as Albion Alloys metal tubes, or 'Plastruct' or 'Evergreen' plastic tube or rod, so that it can be cut accurately and neatly, either a 'straight' cut, or at a 45 degree angle. The tube is fed into the v- shaped 'jaws' and clamped by the little lever at the top, whilst the required length is set against the scale on the side, by sliding the central rod in the relevant direction, then lock it in place. Then just use a razor saw through the desired slot, just like using a mitre block.
The long black thingy on the bottom is the handle, which can of course be hand-held, or clamped in a vise.