NOVO MARK II Original Instructions Manual page 39

Take out the shutter and wash by detergent.
Lock the arm of the shutter
using metal hook.
Unlock the Roasting-glass lock as pics.
To avoid breakage by falling, grab the bottom of the grass by hand.
Unlock the back-side of the lock.
Roasting-glass is caught by grooves, rotate clockwise and release.
Keep the fitting parts upward.
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