What is sag and how do i set it?

Hi guys,
Just bought my first full suspension bike Marin 2006 Rift Zone and have heard more than one person saying about setting the sag and I aint got a clue what they are talking about.
I gather it is something to do with the rear shock set up but after that am lost!!!!
I have a fox float with medium pro pedal on could you help me with what I need to do with the thing please!!
Thanks
Just bought my first full suspension bike Marin 2006 Rift Zone and have heard more than one person saying about setting the sag and I aint got a clue what they are talking about.
I gather it is something to do with the rear shock set up but after that am lost!!!!
I have a fox float with medium pro pedal on could you help me with what I need to do with the thing please!!
Thanks

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http://cjwoods.com/london2paris
Scott Scale 10
Focus Izalco Team
http://www.foxracingshox.com/fox_tech_c ... ock_en.pdf
theres a link to the appropriate manual which describes how to measure and set the amount of sag.
Basically, when you sit on your bike the shock should be compressed by 25% of the overall travel. This will help it react correctly to bumps etc. Measuring the length of the shock with and without you on it (need someone to help no doubt) and then adjusting the air presure in the shock to match 25% of the travel. Does that make sense?
http://cjwoods.com/london2paris
Scott Scale 10
Focus Izalco Team
Thanks for all the advice - I did not get manuals cause I bought the bike second hand from e-bay so thanks for the links to the manuals etc
That makes sense as to how to set and I like the Zip tye idea that works for me!!
Will give you a shout if I get stuck
Cheers fellas!
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