Adapter devices are provided that, when installed on an aircraft seat track break area, allow for the installation and/or positioning of passenger seats thereat. The devices include a main body having two portions. One end of the portion is integrated to a fork-shaped part 2 which defines a half-opening 3. Close to the end of the other portion there is provided a pair of half-tabs which are symmetrically disposed in relation to one another on each side of the body. Pairs of symmetrically disposed semi-circular tabs are provided on the main body. Threaded pass-through holes are located one of the body portions so as to threadably accommodate retaining discs in the form of screw screws heads provided with screws which are installed in the threaded holes.