 Thermate welding of rails. Prior to the weld process, the rail ends must be properly cut so that the gap between the rails has the required size. Also, the rails must be properly aligned by controlling the geometry of the running edge at the top of the rail. The next step is installing the mold with crossable. It is important that there is no gap between the mold parts so that the liquid steel will not flow out of the mold. Moist sand is used around the mold to create the crossable. After applying the high temperature, the sand will be hardened and become ceramic. Before the welding, the rails within the crossable have to be preheated to the required temperature so that the rail properties near the weld after the welding will be as homogeneous as possible. After the preheating, the thermate portion is placed above the crossable and ignited. As a result of the chemical reaction, the liquid steel flows into the mold filling up the gap between the rails. After the initial cooling down and possible post-heating period, the mold with crossable can be removed. The excessive metal around the welded rail has to be removed as well. Obviously, the shape of the rail at and outside the weld is not the same. Therefore, the original shape of the rail head surface will be restored using a grinding machine.