Use a clam to make a quick or temporary change to the inboard/outboard...The clam sits against the outer face of the collar. 2014, Daniela Gomes da Costa, Yihuan Chang, eds., Learn to Row, Fédération internationale des sociétés d'aviron, page 28
The CLAM can be 'clipped on' by the rower with little difficulty, so the load can be changed between alternating headwind–tailwind pieces. 1995, Larry Gluckman, “Rowing News”, in The Independent Rowing News Inc., page 3: