The anti-gravity shield was a device developed by the Ancients to protect ships against powerful sources of gravity such as a black hole. The device could be built with Earth technology but needed a specific power core to run it as it required so much power, that not even a naquadria generator could power it. However, if the wiring was wrong, the wiring would burn out quickly during use. The wiring could be replaced by wiring from a MALP, but it would only last a few minutes before the device burned out for good. The shield is designed to be deployed around a ship and if used as protection against a black hole, it shields the ship against both intense gravity and time dilation effects. However, to interact with anyone outside of the shield bubble on a planet affected by the black hole's time dilation, the shield had to be dropped. While using the shield, a ship can safely jump to hyperspace while within a black hole's radius, but it can be dangerous. (SG1: "A Matter of Honor", "The Cost of Honor")
The device was originally created by the Ancients for an unknown purpose, but given the inscription on the power core, it wasn't for war but peace. Some time in the past, Ba'al got his hands on the device and used it as half of a great weapon he developed: black holes he created with gravity technology. The shield acted to protect his ships from the effects of the black holes he created, but eventually the System Lords rose against him and forced him to never return to Kinahhi where he had his gravity technology. They shattered his shield, allowing him to keep the power core and keeping the rest on Kinahhi with the rest of his gravity technology. On pain of death, the System Lords forbade Ba'al from returning to Kinahhi where the main part of the shield was kept and allowed Ba'al to take the power core which he hid on Asdad as a shrine. The story became a legend among at least the Jaffa on Chulak.
In 2003, SG-1 traveled to Kinahhi where they found out about the gravitational technology there that had been adapted from what had been left behind by Ba'al. Colonel Jack O'Neill became interested in the gravity technology as a possible way to rescue SG-10 from P3W-451 which was being sucked into a black hole, but they were only interested in sharing their sheh-fet technology as a means of conquering Earth. Knowing SG-1 could be a deterrent to their plans, Councilors Damaris and Quadesh of the Kinahhi plotted to get rid of them: after learning of O'Neill's interest in their technology from Ambassador Bill Crawford who overheard O'Neill telling Doctor Daniel Jackson, Quadesh downloaded the plans for the anti-gravity shield from the Kinahhi database and gave them to O'Neill in secret, claiming he was a rebel against the Kinahhi government and committing a suicide bombing to help convince the team. Unknown to the team, he deliberately sabotaged the plans so the wiring would burn out at a critical moment and the device would fail. O'Neill was forced to bring the rest of SG-1 in on the secret as only Major Samantha Carter could build the device, but Carter determined that none of their power sources would work in it. After Jackson figured out that the celling mosaic in the floating city of Tsapan was a black hole, Teal'c remembered the legend about Ba'al and his weapon and they realized the original power source was on Asdad and decided to seek it out. After learning that Crawford's report was going to cause Senator Robert Kinsey to have General George S. Hammond ground SG-1, O'Neill managed to convince Hammond to give them a mission before that time to get them off-world. During that time Carter completed the shield device and Jackson managed to figure out that Asdad was Ba'al's fortress where he conducted gravity research and tortured O'Neill before Lord Yu attacked it, forcing him to abandon it. Having figured out where to find the power source, SG-1 secretly traveled to Asdad and raided the ruined fortress, retrieving the power source and destroying the fortress on their way out in a Tel'tak they stole from it.
Having gotten what they needed for the shield to work, SG-1 traveled to P3W-451 in the Tel'tak. By the time they got there, Carter had gotten the anti-gravity shield up and running and it protected the ship on approach to the planet. However, as they prepared to land and briefly lower the shield so they could rescue SG-10, the wiring burnt out due to the deliberate flaw that Quadesh had put in the plans and the ship crashed. SGs 1 and 10 reunited when SG-10 saw the Tel'tak as their only hope of escape and went to it. Carter figured out she would be able to patch the shield with the wiring from the MALP on the planet long enough for them to get away, but the stellar matter from Vorash's sun finally started to arrive through the Stargate and they were forced to flee before she could repair the device, losing Lieutenant Jonathan Reed in the process. Teal'c worked to keep the ship from sliding into the black hole for as long as possible and managed to do it long enough for Carter to get the shield up again. Teal'c immediately took the Tel'tak to hyperspace, but the strain was too much on the shield and it finally burned out. However, it held long enough for them to get away though they crashed on P3X-500. However, the short time the shield was dropped caused SG-1 to be gone for five months to the rest of the universe. The shield device was abandoned with the ship on the planet and was later destroyed when the Tel'tak crashed into the ocean of Kinahhi. (SG1: "Exodus", "Abyss", "A Matter of Honor", "The Cost of Honor")