Radiator Coolant Drain - 2000 S10 Pick-up

I've reviewed posts related to my problem draining coolant from my S10, 2.2L (4 cyl.) The drain petcock on my vehicle is located on the driver side and is barely visible. On my truck the part is plastic and when viewed from the top tooks like a large tamper-resist screw head; the type that allows a screwdriver to turn only one way. One post I read correctly indentified that a 1/4" square socket will fit the petcock (drain) fitting. The 1/4" square drive fits at the center to open/close the fitting.
Unfortunately, in my case turning the petcock a quarter-turn did not drain the fluid (clogged?). I resorted to removing the lower radiator hose. Just as well - while it's loose I'll go ahead and replace the hose.
I hope this saves some searching. Good luck!

After the 1/4 turn, did you try pulling the plug out?
It slides about 1"