A mounting board is used to adapt a differently sized mechanism or type to the bottom of a chair seat.

The board is attached to the original mountings using the same or longer fasteners. Then the new mechanism is wood screwed to the board.

The mechanism may be moved forward or back on the board without making more holes in the seat bottom. Why move?

The mounting board need not be removed after installation but can remain permanently.

The mounting board if not removed, usually cannot be seen. Painting the edges Black will ensure that, making it virtually unseen.