The adhesive is an alien substance that can patch almost anything.
In "Dipper and Mabel vs. the Future," Ford and Dipper venture into Crash Site Omega to find some alien adhesive in order to patch the Interdimensional rift and prevent it from breaking. Ford warns Dipper to be careful when handling it, as it could "seal up all the orifices in [his] face".
During the search, Dipper's Magnet Gun gets stuck to an hexagonal object which contains the adhesive.
Later, Ford has the adhesive ready and asks Dipper to hand him the Rift so they can finally patch it up, only to find out that Mabel Pines had uknowingly run off with Dipper's backpack, taking the rift inside.
The adhesive reappears and is finally used in "Gravity Falls: Lost Legends", during the tale "Don't Dimention It!", Ford has almacened it in a special weapon, simmilar to a watergun to aid him in sealing the resudual rifts created after Weirdmageddon. But after confusing Anti-Mabel for Mabel, she steals Ford's adhesive and uses it on Stan and Ford sticking them in the ground and later she attacks the other Mabels with it. At the end the Pines manage to recover it and Stan uses it to seal the rift. Military Expert Mabel said that the adhesive sealed all her wounds in her body when she was exposed to it, that, and considering Stan and Ford and every victim from it was unscratched, it means that Ford was exagerating the whole time.
The adhesive is a slimy, bright purple liquid that acts as a powerful glue.
- Back in "Dipper and Mabel vs. the Future", Ford said that the adhesive could "seal up all the orifices in [their] faces", while handling the adhesive, but in "Don't Dimension It!", Anti-Mabel used it indifferently even in direct skin contact with other characters, such as Stan, Ford, Table Mabel or Military Expert Mabel and they're unscratched. According to Military Expert Mabel, the adhesive only healed her wounds, this means that Ford was exaggerating the whole time or he didn't research it properly.