iGaging's Snap Gauge features a small pin for measurement, that can make measurements in almost every nook and cranny of your project.

Some types of depth measurements are easier to take than others. While you can slide the rule of a combo square down into a mortise to find the bottom, how do you do that with a small diameter stopped hole? A Snap Depth Mini Depth Gauge (iGaging, $25 in 2011) makes the task, well, a snap. Use it to measure holes, dovetails, slots and grooves, rabbets ... you name it. The device has a slender, spring-loaded probe. Zero it out with the tool’s base pressed against a reference surface, then slide it over the hole to take a reading. For holes deeper than 1", you get 1" and 2" extension rods to expand the depth-finding range to 4" overall. Here’s a bonus: the Snap also has a mounting lug on the back that could be attached to a separate base. That way, it can double as a dial indicator for evaluating shaft runout, blade flatness or other tasks. Quite versatile.