I recently purchased a Sinar F camera. On the front standard this gadget is attached...I've tried to research what it's for, but haven't found anything out...What the heck is it for?
My first 4x5 was a Cambo SC. It has that button you push and then slide one way to release the bellows and the other to release the lens board. I once slid it the wrong way and fortunately caught my lens about knee high, just before it hit the floor.