I believe they are used as supportive brackets for furniture (corners). They even have little triangle thingies on the backsides to kind of dig in to whatever you are bracing. At five bucks a piece, it is a pretty inexpensive alternative. I was thinking of buying a bunch and using them as presets, as well as one set for run and gun.
They weigh about 5 ounces each; quite light. I will probably go with another bracket. This is all I had lying around the house.
I have lightly filed the edges but because the whole thing looks cast, I really could not feel any sharp edges. I will round them off though. The aluminum is very easy to work with.
So, what can I wrap these things in that will silence them when I am setting them up?