How do I do a leak down teast?

[dnoftz]

I bought a leak down tester on here a few years ago and now I forgot how to use it right.

Does the piston have to be in a certent spot? Top dead or below ports ? any info would be helpfull

 

[Blaaster]

BDC is the best place for the quickest test, but it can be anywhere the pressure will equalise no problems.