A fastening element for attaching to a wall having - a holder element for holding an object; - a contact element having an adhesive surface (21, 121, 221) and a rear side; - a filling passage which leads from the rear side of the contact element to an outlet opening (18, 118, 218) in the adhesive surface (21, 121, 221) of the contact element and via which a flowable adhesive agent can be brought between the adhesive surface (21, 121, 221) and the wall; and - a positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) by means of which the contact element can be positioned at the wall, characterized in that - the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) is configured to bring about a pre-fastening of the contact element at the wall before a final attachment at a desired position; - the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) has a width which is variable in dependence on a spacing from the outlet opening (18, 118, 218); - the width of the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) results from an extent parallel to the adhesive surface (21, 121, 221) and perpendicular to a direction of flow (28a, 28b, 28c, 28d; 128a, 128b, 128c, 128d; 228a, 228b, 228c, 228d; 328a, 328b, 328c, 328d) from the outlet opening (18, 118, 218) through a center of area (25a, 25b, 25c, 25d; 125a, 125b, 125c, 125d; 225a, 225b, 225c, 225d; 325a, 325b, 325c, 325d) of the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d): - the width reduces at least sectionally as the spacing from the outlet opening (18, 118, 218) increases; and - the width is minimal at a maximum spacing from the outlet opening (18, 118, 218). - a holder element for holding an object; - a contact element having an adhesive surface (21, 121, 221) and a rear side; - a filling passage which leads from the rear side of the contact element to an outlet opening (18, 118, 218) in the adhesive surface (21, 121, 221) of the contact element and via which a flowable adhesive agent can be brought between the adhesive surface (21, 121, 221) and the wall; and - a positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) by means of which the contact element can be positioned at the wall, - the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) is configured to bring about a pre-fastening of the contact element at the wall before a final attachment at a desired position; - the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) has a width which is variable in dependence on a spacing from the outlet opening (18, 118, 218); - the width of the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d) results from an extent parallel to the adhesive surface (21, 121, 221) and perpendicular to a direction of flow (28a, 28b, 28c, 28d; 128a, 128b, 128c, 128d; 228a, 228b, 228c, 228d; 328a, 328b, 328c, 328d) from the outlet opening (18, 118, 218) through a center of area (25a, 25b, 25c, 25d; 125a, 125b, 125c, 125d; 225a, 225b, 225c, 225d; 325a, 325b, 325c, 325d) of the positioning element (23a, 23b, 23c, 23d; 123a, 123b, 123c, 123d; 223a, 223b, 223c, 223d; 323a, 323b, 323c, 323d; 423a, 423b, 423c, 423d): - the width reduces at least sectionally as the spacing from the outlet opening (18, 118, 218) increases; and - the width is minimal at a maximum spacing from the outlet opening (18, 118, 218).