dear P2J
you ask a fine question, and just to be sure I got out my 737 manual (200 series, but I doubt much has changed, please corect me if I am wrong).
from the manual:
Manual extension is provided by three emergency landing gear extension handles located under an access door in the cockpit floor. Pulling a handle to is full extension will unlock the uplock on the associated landing gear.
To assure that free fall of the gear is unimpeded by trapped hydraulic pressure, the landing gear handle should be in the OFF position.
I hope this helps. Tongue twister there: unlock the uplock...should be used to find out if pilot is drunk! (kidding to all of you drunk pilots).