A brake shoe that is lockable to a rail head of a rail for securing a unit transportable on rails, in particular a high-voltage device, such as a transformer. To maintain the position of the unit securely on a rail in a simple manner, the brake shoe is provided with a frame designed to clasp around at least portions of the rail head and at least one clamping element movably held in the frame. The brake shoe produces self-retaining clamping of the rail between the frame and the at least one clamping element.

Friction block or layer made of an asbestos free friction material, the friction material including, as composing materials thereof, inorganic and/or organic and/or metallic fibers, at least a binder, at least a friction modifier or lubricant and at least a filler or abrasive, wherein the asbestos free friction material also contains, as an additional composing material or additive, an hydrophobic wax, preferably present from 0.5% to 5% in volume, the asbestos free friction material block or layer possessing a hydrophobicity, defined as the time of absorption within the friction material of a liquid drop formed by 20+/5 L of distilled water, of more than 60 minutes, so that the force to detach the friction block or layer from a metallic surface to which it has been made to stitch electrochemically is lower than 15 Nw.

Friction block or layer made of an asbestos free friction material, the friction material including, as composing materials thereof, inorganic and/or organic and/or metallic fibers, at least a binder, at least a friction modifier or lubricant and at least a filler or abrasive, wherein the asbestos free friction material also contains, as an additional composing material or additive, an hydrophobic wax, preferably present from 0.5% to 5% in volume, the asbestos free friction material block or layer possessing a hydrophobicity, defined as the time of absorption within the friction material of a liquid drop formed by 20+/5 L of distilled water, of more than 60 minutes, so that the force to detach the friction block or layer from a metallic surface to which it has been made to stitch electrochemically is lower than 15 Nw.