Help Striping Engine

Hi ya all
I need some help i have brought an engine. i started to strip it down to clean it up.
I ve got to the bit of taking the timing gear cover off but i can not get the starter dog off because it just turns the whole shaft.
How can i stop the engine from turning so i can get the starter dog off.
please help.
Thank you

Take the starter motor off and wedge a chisel in, haynes says something like that but be careful not to break/damage anything

cheers i will try that. hopefuly that will work.