I've found this to be a handy alternative to a drill press when working with awkwardly shaped pieces of wood or when drilling in tight spots with an angle attachment. For perfectly spaced square holes, you can: (1) drill a groove in the hole, (2) place the drill bit on the hand drill, (3) insert the tip of the drill bit into the groove, (4) slide the guide down toward the wood and finally ( 5) Lock this guide. That works every time. For depth controlled holes without damaging the finish you can: (1) add .500" to the depth of the retaining ring, (2) drill this guide so that the ring rotates against this guide and not the wood. The holes have enough dexterity to not bind the twist drills. A groove along the bottom allows scrap wood to remove the drill while this guide is still clamped.