Gymrex GR-MG 56 Manual De Instrucciones página 24

STEP IV
a) Fasten the backrest (10) and headrest (9) support frames to the main frame
(3). For this purpose, place three reinforcement plates (13) on the support
frames.
b) Place the backrest and headrest on the assembly mounted as above.
All connections of the machine should be fixed and pressed correctly. After
completing the assembly activities, it is allowed to start working with the
machine.