You know those cheap, thin poster frames with the pressure fit edges that always fall off?

They're awful, they always fall apart, but they're SO CHEAP and the next best alternative is several times more expensive.

Well, these little corner brackets solve my problem of the edges falling off my poster frames. They need to be anchored to the wall, but if it's a semi-permanent hanging location it shouldn't be too rough on your walls.

Flip it upside down if you don't want to use supports, and use a good amount of infill on these, since they need to be able to handle a good amount of flex stress.