I must be missing something so simple but its driving me mad..............I have tarpaulin, wire, guitar, hat and can't use anything anywhere!
Spoiler
Interact with the hat in your inventory to find a hook.
I can't believe I missed that!
Errrrrrr stuck again, now got the hammer but once again can't find anything else to do :-\
You can use the hook on its own on the box at the right side of the shed. If you click on the hook + wire combo in your uninventory, you'll untie the hook from the wire.
Thanks I didn't realise I could do that ::)