Although this device is meant more for drywall cutting, I find it to be a useful tool when I'm cutting out narrow, shallow depressions in styrofoam for miniature landscape crafting. When I want to cut down to- and maintain- a specific depth, the guide lends me a really big assist.
Sadly, it's one of those accessories that require the use of collets, rather than a chuck, on the rotary tool. Not a really good thing when I'm constantly changing bits, and want to do it quickly. Oh well...
`Late!