That’s a Crane Hook Block / Bottom Hook Assembly painted blue
What it’s used for:
This is part of a lifting system. It’s used with cranes, hoists, or chain blocks to lift and move heavy loads.
Key parts I can see:
1. Swivel Hook - The big blue hook with the safety latch. The latch stops slings/chains from slipping off. The swivel lets it rotate so the load doesn’t twist.
2. Sheave/Pulley Housing - The flat blue plate on top with the bolt. This is where the wire rope or chain runs through.
3. Shackle Connection - The part between the hook and pulley that connects it all together.