This happened about 4 years ago. I do construction and we start fairly early. Boss got tired of people walking in at 6:05 or 6:03 when we start at 6:00 (even though he was a few minutes late more consistently than any one of us were), so he said “If you aren't standing in front of me at 6 o'clock when we start then I'm docking 15 minutes from your time for the day.”
The next day I forgot my tape measure in my car and had to walk back across the jobsite to grab it, made it inside at 6:01 and he told me he was serious yesterday and docked me 15 minutes. So I took all my tools off right there and sat down on a bucket. He asked why I wasn't getting to work and I said “I'm not getting paid until 6:15 so I'm not doing any work until 6:15. I enjoy what I do but I don't do it for free.”
He tried to argue with me about it until I said “If you're telling me to work without paying me then that's against the law. You really wanna open the company and yourself up to that kind of risk? Maybe I'm the kind to sue, maybe I'm not, but if you keep on telling me to work after you docked my time then we're gonna find out one way or the other.”
He shut up pretty quickly after that and everyone else saw me do it and him cave, so now they weren't gonna take his crap either. Over the next few days guys that would have been 1 or 2 minutes late just texted the boss “Hey, sorry boss. Would have been there at 6:02 and gotten docked, so I'll see you at 6:15 and I'll get to work then.” and then sat in their cars until 6:15 and came in when their time started.
So between people doing what I did or just staying in their cars instead, he lost a TON of productivity and morale because he decided that losing 15 minutes of productivity per person and feeling like a big man was better than losing literally 1 or 2 minutes of productivity when everyone stands around BS-ing and getting material together for the day until about 6:10 anyway.
After a few weeks of that he got chewed out by his boss over the loss of productivity and how bad the docked time sheets were looking and reflecting poorly on him because we were missing deadlines over it, and then suddenly his little self implemented policy was gone and we caught back up.
Worker solidarity for the win. Not one person took his crap and worked that time for free after he tried to swing his weight around on them.
But obviously I was a target after that and only made it two more months before he had stacked up enough BS reasons to get away with firing me when I called in a few days in a row after my mom fell and I took off work to take care of her and monitor her for a while during the day.