Patent attributes
The invention includes an outer frame, fasteners, an inner frame, a supporting body and pressing strips. The outer frame has a surrounding trough. The fasteners are disposed in the surrounding trough. Each fastener has an engaging portion. The supporting body is made of a flexible material and has a loading side and a connecting side. The pressing strips are surroundingly attached on a periphery of the connecting side. An interval is kept between two adjacent pressing strips to provide flexibility. The supporting body covers the front of the inner frame. The pressing strips are fastened onto the rear of the inner frame. The inner frame with the supporting body is embedded into the surrounding trough to engage with the engaging portions of the fasteners.