This is another version of a lock for the MakerGear M2 Z-axis knob, to keep the Z-stage from dropping when the motors are turned off. The problem I've had with other such locks is that I have a tendency to turn on my printer and then hit the "home Z" button without bothering to check if the lock is on or not. If it is, then the Z motor starts hammering away, and usually I have to kill the power and start over. This version is designed so that it stops the Z stage from dropping, but won't stop it from lifting. NOTE: For the M2 dual upgrade, this knob does not allow the extruder assembly to move all the way to the left. See http://www.thingiverse.com/thing:934680 for another version that solves the extruder assembly clearance problem.Prints with no particular issues. As designed, it works with both the older and newer style knobs. The newer knobs are a bit smaller, so it's a little loose on the new knobs and a little tight on the old knobs. If that's an issue, the part can be scaled accordingly. It would be nice if it could clear the extruder mount; as it is, it gets in the way of the extruder going to "home X". Since that's a tight fit, it will take more clever design work than I have time for right now.