Connecting piece of tray-type wire cable channelling sections consisting of U-shaped cross wire bars with a central branch and side branches, and longitudinal wire bars (Vl), where said connecting piece is provided with a front side and a rear side, to tightly fit the cross wire bars (Vt1-Vt2)) located at the ends of two adjacent cable channelling sections (B, B), said connecting piece being generally configured with a W-shaped cross-section, having: - two longitudinal grooves with a C-shaped cross-section, where the said wire bars are fitted; - a central portion which extends and connects the corresponding longitudinal grooves; and - corresponding flanges that extend from the outer edges of the relevant longitudinal grooves to be overlapped at the peripheral area of such wire crossbars of the relevant cable channelling section, wherein: - such connecting piece is generally configured in the shape of an U with a central branch which extends practically covering the whole length of the corresponding central branch of the cross wire bars; and the corresponding side branches that form an angle with the central branch, which is equal to, or greater than the angle formed by the side branches and the central branch of the crossbars of the cable channelling, and each one of the side branches is extended covering fully or partially the corresponding side branch of the cross wire bars; - the flanges corresponding to the side branches of such connecting piece is equal to or smaller than the transverse distance between the adjacent longitudinal bars of the cable channelling, where the said flanges are configured with a lower bevel edge inclined downwards, which allows the fitting between the bars and the connecting piece and acts as an upper stop to avoid the demounting of the connection when vertical forces are applied in an upwards direction, and wherein - the corner portions connecting the central branch and the relevant side branches of the U-shaped connecting piece have been configured with a W-shaped cross section by extending the cross-sections of the relevant side branches and the central branch. - two longitudinal grooves with a C-shaped cross-section, where the said wire bars are fitted; - a central portion which extends and connects the corresponding longitudinal grooves; and - corresponding flanges that extend from the outer edges of the relevant longitudinal grooves to be overlapped at the peripheral area of such wire crossbars of the relevant cable channelling section, wherein: - such connecting piece is generally configured in the shape of an U with a central branch which extends practically covering the whole length of the corresponding central branch of the cross wire bars; and the corresponding side branches that form an angle with the central branch, which is equal to, or greater than the angle formed by the side branches and the central branch of the crossbars of the cable channelling, and each one of the side branches is extended covering fully or partially the corresponding side branch of the cross wire bars; - the flanges corresponding to the side branches of such connecting piece is equal to or smaller than the transverse distance between the adjacent longitudinal bars of the cable channelling, where the said flanges are configured with a lower bevel edge inclined downwards, which allows the fitting between the bars and the connecting piece and acts as an upper stop to avoid the demounting of the connection when vertical forces are applied in an upwards direction, and wherein - the corner portions connecting the central branch and the relevant side branches of the U-shaped connecting piece have been configured with a W-shaped cross section by extending the cross-sections of the relevant side branches and the central branch.