Prefabricated wall including, on the one hand, at least one skin (2; 2') made of a hydraulic material and extending in a plane and, on the other hand, at least one fastening device for temporarily attaching a guardrail to this prefabricated wall, this fastening device: - including: - a support including, on the one hand, anchoring means for anchoring this support into the material of the skin or of one of the skins (2; 2') of the prefabricated wall, on the other hand, a first wing, which extends in a first plane, yet on the other hand, a second wing, which includes at least one hole (8; 8'), and which extends laterally and outwardly with respect to the skin or to one of the skins (2; 2') of this wall as well as, in a second plane, parallel to the first plane, and extending outwardly with respect to this skin (2; 2') and parallel to the plane along which this skin (2; 2') extends, and yet on the other hand, a connecting portion for connecting the first wing and the second wing; - a plate, which includes a guardrail or which includes means for receiving a guardrail, and which includes at least one through hole (11; 11'); - at least one fixing screw (12; 12') designed to pass through the at least one through hole (11; 11') of the plate and to cooperate with the at least one hole (8; 8') of the second wing of the support, in order to attach the plate to the support; - wherein: - the anchoring means consist at least partially of the first wing of the support, whereby at least a portion of this first wing extends inside the skin of the prefabricated wall or of one of the skins (2; 2') of the prefabricated wall, in the first plane, which is at least parallel to the plane in which this skin (2; 2') extends; - said at least one hole (8; 8') of the second wing consists of at least one threaded hole (8; 8'), while said at least one fastening screw (12; 12') is designed to cooperate by screwing with the at least one threaded hole (8; 8') of the second wing of the support. - including: - a support including, on the one hand, anchoring means for anchoring this support into the material of the skin or of one of the skins (2; 2') of the prefabricated wall, on the other hand, a first wing, which extends in a first plane, yet on the other hand, a second wing, which includes at least one hole (8; 8'), and which extends laterally and outwardly with respect to the skin or to one of the skins (2; 2') of this wall as well as, in a second plane, parallel to the first plane, and extending outwardly with respect to this skin (2; 2') and parallel to the plane along which this skin (2; 2') extends, and yet on the other hand, a connecting portion for connecting the first wing and the second wing; - a plate, which includes a guardrail or which includes means for receiving a guardrail, and which includes at least one through hole (11; 11'); - at least one fixing screw (12; 12') designed to pass through the at least one through hole (11; 11') of the plate and to cooperate with the at least one hole (8; 8') of the second wing of the support, in order to attach the plate to the support; - a support including, on the one hand, anchoring means for anchoring this support into the material of the skin or of one of the skins (2; 2') of the prefabricated wall, on the other hand, a first wing, which extends in a first plane, yet on the other hand, a second wing, which includes at least one hole (8; 8'), and which extends laterally and outwardly with respect to the skin or to one of the skins (2; 2') of this wall as well as, in a second plane, parallel to the first plane, and extending outwardly with respect to this skin (2; 2') and parallel to the plane along which this skin (2; 2') extends, and yet on the other hand, a connecting portion for connecting the first wing and the second wing; - a plate, which includes a guardrail or which includes means for receiving a guardrail, and which includes at least one through hole (11; 11'); - at least one fixing screw (12; 12') designed to pass through the at least one through hole (11; 11') of the plate and to cooperate with the at least one hole (8; 8') of the second wing of the support, in order to attach the plate to the support; - wherein: - the anchoring means consist at least partially of the first wing of the support, whereby at least a portion of this first wing extends inside the skin of the prefabricated wall or of one of the skins (2; 2') of the prefabricated wall, in the first plane, which is at least parallel to the plane in which this skin (2; 2') extends; - said at least one hole (8; 8') of the second wing consists of at least one threaded hole (8; 8'), while said at least one fastening screw (12; 12') is designed to cooperate by screwing with the at least one threaded hole (8; 8') of the second wing of the support. - the anchoring means consist at least partially of the first wing of the support, whereby at least a portion of this first wing extends inside the skin of the prefabricated wall or of one of the skins (2; 2') of the prefabricated wall, in the first plane, which is at least parallel to the plane in which this skin (2; 2') extends; - said at least one hole (8; 8') of the second wing consists of at least one threaded hole (8; 8'), while said at least one fastening screw (12; 12') is designed to cooperate by screwing with the at least one threaded hole (8; 8') of the second wing of the support.