Help me please....

Hello guys.......

I am participating in a competition where i have to lift a block with a ring and place it on a wall.

My problem is i can make a hook and pulley system to lift and pick up the block to the required height but i cant release the hook.

Can anyone tell me how to release the hook?

Or can anyone give me some idea on how to do the job in an alternate way without using the hook??

THANKS ALL

How about an actuated lever that lifts the ring out of the hook?

Thanks,i will certainly try it.........