I made this rig several years ago to find where to drill a hole through a bulkhead to allow the passage of a push-pull tube (photo below). It would work find for cables as well. In practice it isn't perfectly rigid, so it can't be perfectly precise. But it is perfectly good enough for most cables or push-pull tubes that need a bit of margin anyhow. You adjust the spine length so that it approximates the length of the push-pull tube in question. I just use whatever piece of 3/4" square steel scrap is about the right length for the spine. Then you tweak the arm for the laser until it points right at the target tube. To use it, you put the target tube is where one endpoint for the push-pull tube, for example at a guide or bellcrank. Then you place the laser pointer end at the other endpoint, like at the next guide or bellcrank. The laser points at the spot on the bulkhead where you need to drill it for the tube to go through. Start by drilling an undersize hole and double-check with a straight rod or a string stretched between the two endpoints, and adjust as necessary. Then drill or cut the hole up to the finished size. We generally use a 1" hole for a 5/8" OD push-pull tube; that allows some misalignment during assembly.