The U frame is a light, single wire frame. It is installed thru the top of the coroplast sign, into the flutes of the plastic. It is held in place by a small clear piece of adhesive backed vinyl to keep it from sliding down the legs of the frame. With the single wire on each side for support the frame will blow around, but is flexible enough to spring back and does not have any welds to break. The U frame is the most common way that political style fold over signs are mounted, but it can also be adapted to make an inexpensive way to mount corrugated plastic signs. It sells for $2.00.