Device for fastening a preferably planar object such as a shelf or seat to a construction such as a wall or floor, comprising a first holding element ,and a second holding element , wherein the second holding element can be connected in a form-locking manner to the first holding element , wherein the first holding element (16, 108, 282 348, 414), which can be connected to the construction or the object , or is integral with the construction or the object, has a C- or U-shaped inner profile , wherein the second holding element , which can be connected to the object or the construction, or is integral with the construction or object, has a C- or U-shaped outer profile and wherein the C- or U-shaped outer profile can be received in a form-locking manner in the inner profile and can be tensioned against the inner profile by means of at least one clamping element , characterized in, that the first holding element comprises a first leg and a second leg as well as a web connecting the legs , 114, 316, 368), wherein the first leg extends at right angles to the web and wherein the second leg comprises a first leg portion or a surface portion which extends straight and at right angles to the web and has an adjoining second leg portion or oblique surface portion which is curved or inclined in the direction of the first leg and extends obliquely with respect to the straight leg portion or the straight surface portion , that the second holding element comprises a first leg and a second leg as well as a web connecting the legs (40, 42; 74, 76; 88, 90, 290, 292, 356, 358), said first leg being straight and perpendicular to said web , said second leg having a first leg portion extending at an obtuse angle α oblique to the web and a second leg portion, adjacent the oblique first leg portion , extending parallel to the first leg, that the at least one clamping element is formed as a screw received in a thread of the first or second leg of the first holding element, wherein a center axis of the clamping element extends parallel to the web, that the at least one clamping element is arranged in the first leg and/or the second leg in the straight leg section and/or the oblique leg section, and that the at least one clamping element is directed against the first leg of the second holding element . that the first holding element comprises a first leg and a second leg as well as a web connecting the legs , 114, 316, 368), wherein the first leg extends at right angles to the web and wherein the second leg comprises a first leg portion or a surface portion which extends straight and at right angles to the web and has an adjoining second leg portion or oblique surface portion which is curved or inclined in the direction of the first leg and extends obliquely with respect to the straight leg portion or the straight surface portion , that the second holding element comprises a first leg and a second leg as well as a web connecting the legs (40, 42; 74, 76; 88, 90, 290, 292, 356, 358), said first leg being straight and perpendicular to said web , said second leg having a first leg portion extending at an obtuse angle α oblique to the web and a second leg portion, adjacent the oblique first leg portion , extending parallel to the first leg, that the at least one clamping element is formed as a screw received in a thread of the first or second leg of the first holding element, wherein a center axis of the clamping element extends parallel to the web, that the at least one clamping element is arranged in the first leg and/or the second leg in the straight leg section and/or the oblique leg section, and that the at least one clamping element is directed against the first leg of the second holding element . <EOS>