The Middleman Cryogenics Vault is a room located inside Middleman HQ, and located directly off Ops behind a thick, sealed steel door. Inside, people frozen by O2STK are kept until they need to be unfrozen. Subjects may be unfrozen by entering a code on a security panel outside the Cryogenics Vault. The process of unfreezing causes Ops to shake so much that objects on the walls drop to the floor.
The only known person to be frozen in this manner is Guy Goddard, the 1969 Middleman, who elected to freeze himself when he suspected that his arch-nemesis, The Candle, had faked his own death. Guy ordered Ida to unfreeze him if the Candle ever reared his ugly head again. In 2009, when it appeared that the Candle had indeed emerged from hiding, Ida unfroze Guy Goddard to continue the fight.
It is unclear whether Middlemen have ever frozen people against their will and sealed them in the Vault, or if any Middlemen besides Guy have elected to become what Wendy Watson called "Middle-sicles".