Parrels were common to 17th, 18th, and some 19th century ships. The ribs (battens) and trucks (rollers) were strung together on rope trusses. The ends of the truss were secured around the yard, while the ribs and trucks were passed around the body of the mast.
I installed 3 Ribs. The Trucks (Beads) go vertical along the Parrel. The Loop on the end is so I can run the line around the Spar to secure it.