Self-clamping device suitable for temporarily securing a material without damaging its surface with a force proportional to the material's weight and/or to any pulling force exerted on the material wherein the device includes a casing having an opening for said material, the casing being formed with two side walls diverging away from the opening, and at least one roller in the casing which is mounted rotatable and slidably along one of the walls and which positively urged towards the opening and the other wall so that when the material is inserted into the opening the roller is pushed away from the opening, any pulling force exerted upon the material thereby drawing the roller toward the opening so that as the roller moves along the diverging wall it moves toward the other wall so as to produce a wedging effect, and as a consequence thereof keeping the material pinched by the roller with a clamping force whose strength is in proportion to that of the pulling action.