The board with the cord is what anchored the trike to the floor. The light-colored L-shaped wood prevented the trike's wheels from twisting.
Both pieces are screwed to the plywood floor.
Another photo shows the anchoring component in more detail.

The long boards at upper right are the ramp for loading and unloading the unfolded trike. "X"s on the blue tape show where to place screws for attaching things to the floor.