How to get the Nikon F4 and F5 shutter to work with the back open.

I wonder how can we get the Nikon F4 and F5 shutter to work when the back is open or removed in order to test the shutter speed? On some camera like the F3 I just need to have a switch pushed in but it seems the F4 and F5 need more than that.

F100 and lower numbers, the latch has to be up. There is a tab to push and the latch pops up.

That's probably also the case with the F-801...

Nikon F4 set the shutter to M. Open or remove the back. Place the camera with the open back facing you. Camera on. locate the tiny pin in the upper left of the top groove the back fits into. Using your left hand, hold the pin down with your finger or thumb nail. With your right hand operate the shutter. Care not to interfere with the shutter curtains.