From The Stargate Omnipedia
Heavy gravity field
Heavy gravity prison cell
Experimental technology developed by Baal
, installed within many of his prison cells and his torture chamber inside his outpost fortress. For prison cells, the heavy gravity fields keep prisoners contained, preventing the need for cell doors and locks. Status of the field inside prison cells can be determined by ornate dagger-shaped architecture imbedded into two walls of the cell which would shift positions as the gravity status changed.
For the torture chamber, the heavy gravity in the room provides much pleasure for the System Lord
, as he is able to allow his daggers to fall into the well-defined field by just a raise of his wrist, letting the weapons pierce any desired location on the subject. It is also useful for delivering liquid poisons and their antidotes by the same means. The rear wall of the torture room can break away into a dark abyss where the prisoner is thrust.
If power was knocked out of the base, the artificial gravity fields would fail almost immediately. This is perhaps why the system is not in wider use among the Goa'uld, because all prisoners are instantly free.
Abyss - O'Neill is placed in a heavy gravity torture room where he is interrogated by Baal and killed over and over again, then revived and returned to a heavy gravity cell.