Connection member and a wall-mountable bracket provided with an elongated projection member for connecting a wall-attachable body, having an elongated hole for receiving the connection member, to the wall-mountable bracket during use projecting away from a mounting wall along a projection member axis, the projection member therein being insertable into an insertion space of the connection member through an insertion opening, the connection member comprising: an elongated, tubular body having a tubular wall comprising the insertion space, the tubular wall and the insertion space extending along a connection member axis alignable with the projection member axis when the projection member is inserted into the connection member, wherein the tubular body, when viewed along the connection member axis in a direction away from the mounting wall, comprises a proximal end zone, provided with the insertion opening, an intermediate zone and a distal end zone, wherein an inner diameter of the tubular wall in the proximal end zone and the distal end zone is equal to or larger than an outer diameter of the projection member, wherein the intermediate zone is provided with slits extending parallel to the connection member axis, the slits dividing the tubular wall in the intermediate zone into multiple, elongated wall segments, the elongated wall segments being made of a resilient material, wherein a radial wall thickness (t) of the elongated segments is so chosen that, when the projection member is not inserted into the connection member, an inner diameter of the tubular wall in the intermediate zone is smaller than the outer diameter of the projection member, whereas, when the projection member is inserted into the insertion space, the elongated segments are pushed outwardly in radial direction by the projection member, wherein an outer diameter of the segments is equal to an outer diameter of the tubular wall in the proximal end zone and the distal end zone, wherein the tubular wall has a constant-diameter outer contact surface, when viewed along the connection member axis, wherein the outer surface engages the wall-attachable body in a clamping manner. an elongated, tubular body having a tubular wall comprising the insertion space, the tubular wall and the insertion space extending along a connection member axis alignable with the projection member axis when the projection member is inserted into the connection member, wherein the tubular body, when viewed along the connection member axis in a direction away from the mounting wall, comprises a proximal end zone, provided with the insertion opening, an intermediate zone and a distal end zone, wherein an inner diameter of the tubular wall in the proximal end zone and the distal end zone is equal to or larger than an outer diameter of the projection member, wherein the intermediate zone is provided with slits extending parallel to the connection member axis, the slits dividing the tubular wall in the intermediate zone into multiple, elongated wall segments, the elongated wall segments being made of a resilient material, wherein a radial wall thickness (t) of the elongated segments is so chosen that, when the projection member is not inserted into the connection member, an inner diameter of the tubular wall in the intermediate zone is smaller than the outer diameter of the projection member, whereas, when the projection member is inserted into the insertion space, the elongated segments are pushed outwardly in radial direction by the projection member, wherein an outer diameter of the segments is equal to an outer diameter of the tubular wall in the proximal end zone and the distal end zone, wherein the tubular wall has a constant-diameter outer contact surface, when viewed along the connection member axis, wherein the outer surface engages the wall-attachable body in a clamping manner.