HOMCOM A90-105 Assembly Instructions Manual page 9

Installation diagram
Step 6: install parallel bars
1) hole alignment, the top with M6*20 screw through,
place arc gasket, with M6*15 hexagon screw fastenting
2) Bottom end fastened with M8*40 hexagon screw
through M8 nut.
Step 7: install backrest lever
1) the size of the inner and outer hole of the backrest
pipe is not consistent, the large hole is installed
inwardly, with M8*15 semicircle head screws
into the fastening.