- take the grating that was in the instrument to the grating room on the NW side of the dome and replace it in its box
- select the desired grating from its box and take it out to the telescope
- back at the telescope, check that ensure the grating is orientated correctly (2 bolts on 1 side, 1 on the other) before attempting to insert it
- keep the grating level as you insert it, applying firm but gentle pressure until it's flush with the edges of the grating holder frame
- keep hold of the handle and apply gentle upward pressure while you tighten the bolts
- if any of the bolts feel stiff or awkward during tightening, gently wiggle the grating a bit (the bolts should turn quite easily)
- continue tightening until all 3 bolts are fully secure (and can turn no further)
- with all 3 bolts screwed in fully, close the hatch and lock the quarter-turn fasteners