A door operator assembly comprising: at least one component comprising at least one retaining shoulder ; a back plate configured to form an interface for attaching said at least one component to a wall; and at least one clamp for attaching the component to the back plate , said clamp comprising two clamp members , the clamp members being connected by a fastener configured to apply a force at least in a direction which brings the clamp members closer together, wherein each clamp member is configured to cooperate with the retaining shoulder of the component such that movement of the clamp members towards each other also moves each clamp member into contact with a respective surface of the back plate securing the component to the back plate , wherein said clamp further comprises a resilient member configured provide a biasing force pushing the clamp members away from each other, and wherein each clamp member comprises a retaining lip arranged distally on each clamp member , said retaining lip being configured to cooperate with the respective surface of the back plate , wherein said at least one retaining shoulder of said component is on a side of the component configured to face in the longitudinal direction of the back plate , and wherein a distal portion of the retaining shoulder is configured to fit between and cooperate with the clamp members of the clamp to secure the component to the back plate , and wherein the back plate comprises a rear side intended to face the wall and a front side opposite the rear side , wherein the at least one component is mountable to the front side by means of the at least one clamp and the at least one retaining shoulder arranged on the at least one component , and wherein the back plate comprises surfaces facing the front side and extending longitudinally along at least a portion of the back plate . at least one component comprising at least one retaining shoulder ; a back plate configured to form an interface for attaching said at least one component to a wall; and at least one clamp for attaching the component to the back plate , said clamp comprising two clamp members , the clamp members being connected by a fastener configured to apply a force at least in a direction which brings the clamp members closer together, wherein each clamp member is configured to cooperate with the retaining shoulder of the component such that movement of the clamp members towards each other also moves each clamp member into contact with a respective surface of the back plate securing the component to the back plate , wherein said clamp further comprises a resilient member configured provide a biasing force pushing the clamp members away from each other, and wherein each clamp member comprises a retaining lip arranged distally on each clamp member , said retaining lip being configured to cooperate with the respective surface of the back plate , wherein said at least one retaining shoulder of said component is on a side of the component configured to face in the longitudinal direction of the back plate , and wherein a distal portion of the retaining shoulder is configured to fit between and cooperate with the clamp members of the clamp to secure the component to the back plate , and wherein the back plate comprises a rear side intended to face the wall and a front side opposite the rear side , wherein the at least one component is mountable to the front side by means of the at least one clamp and the at least one retaining shoulder arranged on the at least one component , and wherein the back plate comprises surfaces facing the front side and extending longitudinally along at least a portion of the back plate . <EOS>