to prevent the entry of water into the support box 1 it is useful to seal the first and second ends of the box by providing another flat bar extending across the ends of the flat bars 4 and 5 flat bars 4 and 5 have bores 28 extending through them with the bores spaced apart in the direction between the first and second ends of the support box 1 the bores 28 are used for the assembly of the tongue rail device to the switch after the tongue rail support box 1 is assembled the upper surface of the slide plate 2 is machined by chipping and grinding so that the part of the tongue rail supported on and displaceable over the surface of the slide plate is uniformly supported tongue rail 10 is formed from a solid section and extends between a first end and a second end and has a base 12 at its second end which has a height comparable to that of an inserting rail 15 extending from the second end of the tongue rail at the second end the base 12 is welded to the inserting rail 15 as indicated base 12 contains a bore 28 spaced closely from the base 12 of the tongue rail 10 in the direction toward the first end is a spring location 13 so that the tongue rail can be placed against.