The bellows are "pumped" by using a lever. The lever pivots on a simple "hook and eye" arrangement. The hook is mounted on the lever and the eyelet is on the cross bar of the bellows rack.  I mounted the eyelet to one side of the cross bar and the hook about 1/3 up the length of the lever.

      A rope connects the end of the lever to the bottom board of the bellows.  This is a good opportunity to make some fancy wrought fittings, but store bought eyelets will work, too.  Pull the rope tight to force the lever into the highest position.  That, combined with the pivot eyelet set off to one side, will keep the lever up and out of your way when you are not actively pumping the bellows.