The blocks pictured were made to hold the main tubes parallel to the main spar after the main pivot bracket was bolted in and the assembly tightened in. The blocks were simply made to slide into the sissor opening and thus squared the tube to the main in order to locate the aft pivot location. Then add a combination of 24 "squares to the spar to provide a referance to measure for the up and down location of the aft main pivot bracket .
