Today, at my lesson, my teacher observed that when working on something just past my technical ability, my bow track tends to creep upwards, eventually over the foot of the fingerboard. This is neatly evidenced by the collection of rosin dust there. After using his bow to nudge mine back towards the bridge a couple of times he stopped me and produced a C-Clamp.
Not a traditional screw-type C-Clamp but rather one of those trigger activated jobs with soft(er) rubber pads on the business ends of the clamp. Here’s the one I bought for myself after the lesson.
With the affixed to the foot of the fingerboard as shown below, you now have a fence to prevent your bow from wandering too high. While it is hard to see in this picture, there is plenty of clearance between the rail of the clamp and the strings. Also, note that the handle is toward the player’s left so as to be out of the way of the right hand when playing at the frog.
I’ve only used it briefly and it does prevent you from bowing over the fingerboard. It also is quite distracting. In an effort to stop watching my left hand fingers I had taken to watching the bow on the string as I was playing. Now there’s a piece of hardware in the way. I guess it is time to learn to play without watching at all, in addition to managing my wandering bow track.