Compression members are used to keep pressure against the outside face of the case from reaching the packed bicycle. After inserting these into your travel case, pressure is kept away from the packed bicycle by transferring loads from one side of the case to the other side through a 1/2" PVC plastic pipe which is held in place by two plastic disks.
The disks can move sideways in the case to avoid added pressure against the bike if it shifts. To use this device, the first plastic disk is either placed in the bottom of the case before packing or once it's packed, the disc is slipped between the paced items to the bottom. After the bike is completely packed, a plastic pipe is inserted into the socket of the disk lying on the bottom of the case. The final step is to slip the second disk onto the top end of the pipe.