A new term for me. Never heard of it before.
https://mitmuseum.mit.edu/collections/object/HH.5.07163 or see drawing #14 here: https://herreshoff.info/Menu/index.h...5_Reliance.htm
The drawing says they are for the topsail yard and club. Do you suppose they were saddles to keep them in alignment with the topmast and gaff?