Inspired by the newly-added pics of the patriotic drums...

I've never really taken a good look at how the old rope-tensioning system actually works. It seems that it would be difficult to get enough tension to get the heads tight....but I know there must have been some method to how those little leather things were designed so that they would stay in place.

Does anyone have some detailed information or illustrations of how they work? What were the "tricks" of tuning them?Thanks