My angle grinder won’t fit in there. It’s sitting in a weird spot. I tried holding it in place and using a ratchet on the top but nothing budges.even with WD40 to try and loosen it. Literally the only thing holding the seat in. I’ll just have to keep trying. Thanks.
Vise grips could work or if you can wedge something on the metal gripers that would keep it from spinning. Those go into a hole and when you tighten the bolt it pulls the metal and grips onto the hole it is in. Looks like the anchor did not grip good enough and it is spinning. A orbital cutting tool might work in that area but thats my only other idea.
Looks like just a bolt head and washer on the top of this. They make long extensions for socket wrenches, which should let you access the bolt head (that's how they got it in in the first place, most likely). That thing is a threaded insert welded in place, so you don't need to worry about holding it with a wrench at the same time.