How Were the Rockets Held Up?

How exactly were the rockets held in place when they were on their
launch pads during the Gemini and Apollo missions? They simply didn't sit
on their engines. How did the launch pad hold up so much weight?

Also, when the rocket engines were ignited, did the launch pads hold the
rockets down for a few seconds to build up a certain amount of energy before
the pad released it?

I just got done watching the DVD set Project Gemini - A Bold Leap
Forward. A three DVD set produced by Spacecraft Films. I picked it up at
my local Sams Club for only $15.00 A great price considering all the
footage that's contained in the set. It has every launch from the Gemini
missions.

I thought it was pretty cool how they point the rocket up in a cradle.
But I'm wondering how they hold it up after it's sitting up and at what
point they release it after the engines have ignited?

Thanks!