The Jumpgate is a massive device developed by the Federation in the year 2379, spanning three to four hundred meters across.
All known Jumpgates have been used for the specific purpose of establishing intergalactic travel between the Milky Way and Pegasus galaxies, permitting the rapid passage of Starfleet's starships across intergalactic distances. (Star Trek: George Hammond; Star Trek: Intrepid)
Jumpgates are comprised of 90 individual segments, which are interlinked by a powerful energy field, the blocks are constructed individually.
Thanks to the information provided by Dr. Daniel Jackson, Carter developed a way to dial a Jumpgate using Federation technology.
The only known means of destroying a Jumpgate is to break the chain of connecting segments prior to its completion, disrupting the energy field before the singularity that will serve as its power source can be formed.
However, it is possible to render a Jumpgate unusable, as, there is no way to shut down an incoming wormhole.