A drill floor device has two or more mouseholes for assembly and disassembly of pipe string sections. The mouseholes are arranged to be displaced underneath the drill floor by a drive system and positioned under a hole or an opening in the drill floor. At least one of the mouseholes is provided with an elevator arranged to raise and lower a pipe or a pipe string section located in the mousehole, between an upper working position in which the upper end of the pipe/pipe string section projects above the drill floor and a lower position of rest in which the upper end of the pipe/pipe string section is below the drill floor.