I started this project with a full tank and never reading the instructions. That’s on me.
Before I mess this up, there’s four threaded pucks and one style bushing I have never seen before.

Is the rubber just slipped into the hole like a grommet?
There’s no fastener on the top side so that’s cool. Is there anything really holding it there? When I did read the instructions, it’s still not there.
It’s probably so simple once I get to it I bet.
Some pro tips would be nice. Carriage bolts would be nice for the ones in the bed floor but I’m not going to the hardware store now.
Before I mess this up, there’s four threaded pucks and one style bushing I have never seen before.
Is the rubber just slipped into the hole like a grommet?
There’s no fastener on the top side so that’s cool. Is there anything really holding it there? When I did read the instructions, it’s still not there.
It’s probably so simple once I get to it I bet.
Some pro tips would be nice. Carriage bolts would be nice for the ones in the bed floor but I’m not going to the hardware store now.