This was mentioned earlier and thankfully, with a model that integrates a thumb blade lock system, it is very simple to wrap your head around. Here is the deal; a tape measure is designed to be operated with one hand (not including the blade). So, activating the thumb lock will be as easy as extending the blade to your desired position and then flipping it into the lock position. It really is as simple as that. But, remember, to extend it again or retract it you must flip the switch back down. Of course, look for tape measure models that make this easier as if you can’t use your thumb, it may be a nuisance in the long run.