Installation element for a device for the treatment, in particular the humidification, purification and/or cooling, of a useful fluid, in particular a gas e.g. air, by means of a working fluid, in particular e.g. water, and preferably for a gas treatment device operated according to the cross-flow principle, in particular in the form of a heat exchanger as, e.g., a shower cooler for cooling tower, comprising - at least one grid mat provided with - an upper side and a lower side, as well as two mutually parallel longitudinal edges and two transversal edges extending transversally thereto, - a first set of upper grid bars extending at the level of the upper side, as well as parallel to the longitudinal edges and extending from one transversal edge to the other transversal edge, - a second set of lower grid bars extending at the level of the lower side, as well as parallel to the longitudinal edges and extending between the transversal edges, - upper connecting bars between two respective adjacent upper grid bars, said connecting bars extending at the level of the upper side, - lower connecting bars between two respective adjacent lower grid bars, said connecting bars extending at the level of the lower side, - wherein the upper and the lower connecting bars (44, 48), seen in the direction of the extension of the grid mat between its longitudinal edges, are arranged in alternate succession, and - intermediate connecting bars extending from the upper to the lower side between a respective upper grid bar and the lower grid bar closest thereto, - wherein, at their ends arranged at at least one of the two transversal edges, the lower grid bars are provided with skid sections directed to the upper side of the grid mat in an inclined or curved shape, said sections serving to facilitate a shifting of the grid mat in the direction of the grid bar extension relative to a substrate or over the same. - at least one grid mat provided with - an upper side and a lower side, as well as two mutually parallel longitudinal edges and two transversal edges extending transversally thereto, - a first set of upper grid bars extending at the level of the upper side, as well as parallel to the longitudinal edges and extending from one transversal edge to the other transversal edge, - a second set of lower grid bars extending at the level of the lower side, as well as parallel to the longitudinal edges and extending between the transversal edges, - upper connecting bars between two respective adjacent upper grid bars, said connecting bars extending at the level of the upper side, - lower connecting bars between two respective adjacent lower grid bars, said connecting bars extending at the level of the lower side, - wherein the upper and the lower connecting bars (44, 48), seen in the direction of the extension of the grid mat between its longitudinal edges, are arranged in alternate succession, and - intermediate connecting bars extending from the upper to the lower side between a respective upper grid bar and the lower grid bar closest thereto, - wherein, at their ends arranged at at least one of the two transversal edges, the lower grid bars are provided with skid sections directed to the upper side of the grid mat in an inclined or curved shape, said sections serving to facilitate a shifting of the grid mat in the direction of the grid bar extension relative to a substrate or over the same. - an upper side and a lower side, as well as two mutually parallel longitudinal edges and two transversal edges extending transversally thereto, - a first set of upper grid bars extending at the level of the upper side, as well as parallel to the longitudinal edges and extending from one transversal edge to the other transversal edge, - a second set of lower grid bars extending at the level of the lower side, as well as parallel to the longitudinal edges and extending between the transversal edges, - upper connecting bars between two respective adjacent upper grid bars, said connecting bars extending at the level of the upper side, - lower connecting bars between two respective adjacent lower grid bars, said connecting bars extending at the level of the lower side, - wherein the upper and the lower connecting bars (44, 48), seen in the direction of the extension of the grid mat between its longitudinal edges, are arranged in alternate succession, and - intermediate connecting bars extending from the upper to the lower side between a respective upper grid bar and the lower grid bar closest thereto, - wherein, at their ends arranged at at least one of the two transversal edges, the lower grid bars are provided with skid sections directed to the upper side of the grid mat in an inclined or curved shape, said sections serving to facilitate a shifting of the grid mat in the direction of the grid bar extension relative to a substrate or over the same.