The sous chef had a claw hammer on the wall, “in case any customer gets too touchy with the servers” was his reason.

That was me too except it was literally a comically large spoon

Management does everything in their power to split the restaurant vertically into two competing groups. The second both FOH and BOH turn that split into a horizontal one between themselves and management it becomes much much harder for them to fuck you over or retaliate against you. Capitalism is pathologically incapable of seeing the long-term and always prioritizes short-term profit, so even if it's not a formal union or strike the threat of even an afternoon of lost profit is often just enough to act as a shield. Remaining vigilant is very necessary, they'll try every subtle trick they can and the staff needs to be an immovable object in the face of it every single time. A hard "do what we say or we all walk this second" stance (ideally in less blunt and more plausibly deniable phrasing) can really put management in a deadlock. Having the chance to look my boss in the eye and say "hey, wouldn't it really suck if no one showed up on our busiest and most profitable day of the year?" was fucking euphoric.

Obviously this isn't legal or unionization advice, just stating how we ran the show at my last job. By the time I left the only purpose management really served was as cover. They kept up appearances because "we have absolutely no control over them, every decision is made by the staff, and our jobs are near-useless at this point" isn't a very good thing to say to a stingy cost-cutting boss if you want to keep your job, and we were fine with them taking the credit as long as it translated to regular raises and the owner was kept in the dark.