Tighten or loosen hose clamps in hard-to-reach places without worrying about the driver slipping off the nut. SMC Corporation designed their locking nut driver to lock onto a nut with the flip of a lever.
These nut drivers come in SAE sizes 1/4″ and 5/16″ and in metric sizes 6mm and 7mm. The common driver length sold right now is 10″, but SMC says they’ll be available in 7″ and 20″ versions also.
Snap-on slaps their Blue Point brand on these tools and sells ’em for $19 to $22 for a single driver, or $40 for a two-piece SAE or metric set. Tool Shack and Garret Wade sell the SAE driver set for a little less — about $30.