A holding frame arrangement (10, 20, 30, 40, 50) for a plug connector for receiving similar and/or different modules, comprising: a base frame (11, 21, 41, 51) adapted to receive a module, wherein the module is insertable in a plug-in direction of the plug connector into the base frame (11, 21, 41, 51) and a fixing element (12, 22, 32, 42, 52) adapted for adding in the plug-in direction to the base frame (11, 21, 41, 51) provided with a received module and for fixing to the base frame (11, 21, 41, 51) such that the base frame (11, 21, 41, 51) and the fixing element fixed to it (12, 22, 32, 42, 52) together define a fixing window (13, 23, 33, 43, 53) for engaging a fixing lug of the received module in order to fix the module in place, wherein the base frame (11, 21, 41, 51) and the fixing element (12, 22, 32, 42, 52) are designed to fix in place with a form fit, wherein the fixing element (12, 22, 32, 42, 52) has at least one fixing arm (15, 25, 35, 35', 45, 55) with an engagement hook (16, 26, 46) for engaging an undercut or a recess (27, 47) in the base frame (11, 21, 41, 51), wherein a) the movable fixing arm (15, 55) is designed for moving the engagement hook parallel to a plane defined by the fixing window (13, 53) or, b) the movable fixing arm (25, 35, 35', 45) is designed for moving the engagement hook (26, 46) transversely to a plane defined by the fixing window (13, 23, 33, 43, 53), wherein the engagement hook and the region of the base frame past which the engagement hook is moved when fixing it in place are designed so that the fixing arm does not project beyond a side surface of the base frame during said movement. a base frame (11, 21, 41, 51) adapted to receive a module, wherein the module is insertable in a plug-in direction of the plug connector into the base frame (11, 21, 41, 51) and a fixing element (12, 22, 32, 42, 52) adapted for adding in the plug-in direction to the base frame (11, 21, 41, 51) provided with a received module and for fixing to the base frame (11, 21, 41, 51) such that the base frame (11, 21, 41, 51) and the fixing element fixed to it (12, 22, 32, 42, 52) together define a fixing window (13, 23, 33, 43, 53) for engaging a fixing lug of the received module in order to fix the module in place, wherein the base frame (11, 21, 41, 51) and the fixing element (12, 22, 32, 42, 52) are designed to fix in place with a form fit, wherein the fixing element (12, 22, 32, 42, 52) has at least one fixing arm (15, 25, 35, 35', 45, 55) with an engagement hook (16, 26, 46) for engaging an undercut or a recess (27, 47) in the base frame (11, 21, 41, 51), wherein a) the movable fixing arm (15, 55) is designed for moving the engagement hook parallel to a plane defined by the fixing window (13, 53) or, b) the movable fixing arm (25, 35, 35', 45) is designed for moving the engagement hook (26, 46) transversely to a plane defined by the fixing window (13, 23, 33, 43, 53), wherein the engagement hook and the region of the base frame past which the engagement hook is moved when fixing it in place are designed so that the fixing arm does not project beyond a side surface of the base frame during said movement. a) the movable fixing arm (15, 55) is designed for moving the engagement hook parallel to a plane defined by the fixing window (13, 53) or, b) the movable fixing arm (25, 35, 35', 45) is designed for moving the engagement hook (26, 46) transversely to a plane defined by the fixing window (13, 23, 33, 43, 53), wherein the engagement hook and the region of the base frame past which the engagement hook is moved when fixing it in place are designed so that the fixing arm does not project beyond a side surface of the base frame during said movement.