Sometimes I use C-clamps to fasten things together that need to stay together for a while. Like, until the glue cures.
So, since the shop is shared with non-readers who would only be enraged by the presence of a note, I propose to make a C-frame clamp which can be padlocked in position. (Note this is not the vise-grip style, which is an over- center toggle lock. The person who suggests that it is, or should be, shall be berated mercilessly. As will the person who refers to it as a "vice-grip".)
Looks and acts identically to a regular C-clamp, with the exception of the cross-handle. The handle is missing. It is replaced by a splined shaft, several inches long; the new style handle is a bent metal piece which curves up away from the clamp. After tightening said handle as much as you wish, slide the handle off the splines and then put it back on upside-down, in a position where it is near to the frame of the clamp.
Put the shackle of a padlock through the hole in the end of the handle, and lock it around the frame of the clamp.
Note that this lock is mainly a deterrent to stupidity and accidents. It is not a high security solution.
I am betting the worldwide market for this device would be over a dozen.-- lurch, Aug 13 2013 This makes no sence to me at all, please give better explenation and a drawing !-- zeno, Aug 14 2013 Makes sense to me. An interim bodge would be a bit of thread locking compound; the kind that is difficult to overcome without heating.-- spidermother, Aug 14 2013 random, halfbakery