The Removable Frame Clamp Receiver (RFCR) or “blue lock” is the final component of a DAESSY Frame Clamp Assembly, the parts of the mount kit that stay on the wheelchair at all times.
The RFCR is the receiver “groove” that accepts the Removable Outer Piece’s “tounge” attached to the bottom of the vertical post.
Attaching it is not hard but there are a few little tricks, the following video shows how to go about