measuring

I got a small dilemma with regards to measuring net height. Usually you do want to have the net as tight as possible and with the correct height. I find this impossible to achieve if you measure both at the net posts and then in the middle, there will always be a small difference? I usually...

Hi! I'm searching for an instrument or a tool for measuring of table tennis rubbers (no not a simple ruler or similar):p Maybe a magnifying glass with some measurement involved but built like one piece etc. Anyone have any ideas? DHS TT measurement = too expensive:( Thanks in advance Inkognito