timing belt
the 13mm hex nut holds the cambelt tensioner bearing onto the block,
note the direction of belt mounting.
ideally crank the engine until all the belt timing marks and pulley marks align,
then it's safe to remove the belt,
if timed correctly there should be no THROW of the camshaft, so the pulley will stay still while the belt is changed.
I use the pliers to pre-load the belt tensioning pulley