By the time our tetreaches the DEVAR-TOI in the final book of the Dark Tower series, the Beams guarded by RAT and FISH, BAT and HARE, EAGLE and LION, and DOG and HORSE have all collapsed, and we can assume that their Positronics Guardians have already landed on the celestial junk pile. The only two guy-wires left holding the Tower in place are our tet's Beam - the BEAR-TURTLE - and Gan's Beam - the ELEPHANT-WOLF.
Robin Furth. Stephen King's The Dark Tower. The Complete Concordance