A method for laying down and tensioning a waterproofing liner on a surface of a hydraulic work , such as, for example, a canal, a dam, a water basin, or a hydraulic tunnel, wherein the waterproofing liner is fastened, tensioned and made to sealingly adhere to the surface of the hydraulic work by sealingly clamping the waterproofing liner by a plurality of locking assemblies , wherein each locking assembly comprises a lower metal section bar anchored to the surface of the hydraulic work , and an upper metal section bar that conforms to the lower section bar ; and wherein the waterproofing liner is sealingly clamped between the lower section bar and the upper section bar ; said method being characterised by the steps of a) configuring each lower section bar , or an additional elongated anchor element , with a set of anchor holes at a plurality of anchoring zones , in axially spaced apart positions; b) marking anchoring zones on the surface of the hydraulic work with a set of reference marks in positions corresponding to the positions of the anchor holes of the anchoring zones of the lower section bar , or additional anchor element ; c) perforating the surface of the hydraulic work at at least one reference mark of the anchoring zones of the surface of the hydraulic work; d) positioning each lower section bar , or additional elongated anchoring element , aligning the set of the anchor holes of each anchoring zone of the section bar with the perforations made at each anchoring zone of the surface of the hydraulic work ; e) anchoring the lower section bar , or the additional elongated anchor element , to the hydraulic work , by anchoring devices passing through said anchor holes aligned to the perforations made at the reference marks ; and f) laying down, anchoring and tensioning the waterproofing liner , connecting the upper section bar to the lower section bar of each locking assembly , sealingly clamping the waterproofing liner between opposite slanted flat walls (13; 14) of the lower section bar and the upper section bar . a) configuring each lower section bar , or an additional elongated anchor element , with a set of anchor holes at a plurality of anchoring zones , in axially spaced apart positions; b) marking anchoring zones on the surface of the hydraulic work with a set of reference marks in positions corresponding to the positions of the anchor holes of the anchoring zones of the lower section bar , or additional anchor element ; c) perforating the surface of the hydraulic work at at least one reference mark of the anchoring zones of the surface of the hydraulic work; d) positioning each lower section bar , or additional elongated anchoring element , aligning the set of the anchor holes of each anchoring zone of the section bar with the perforations made at each anchoring zone of the surface of the hydraulic work ; e) anchoring the lower section bar , or the additional elongated anchor element , to the hydraulic work , by anchoring devices passing through said anchor holes aligned to the perforations made at the reference marks ; and f) laying down, anchoring and tensioning the waterproofing liner , connecting the upper section bar to the lower section bar of each locking assembly , sealingly clamping the waterproofing liner between opposite slanted flat walls (13; 14) of the lower section bar and the upper section bar . <EOS>