A closure piece (100, 445, 520, 715, 860) adapted for installing the track of a sliding door, comprising: a bottom plate (120, 430, 515, 620, 745, 855); a front plate (115, 435, 750, 865) coupled along a bottom edge to a front edge of the bottom plate (120, 430, 515, 620, 745, 855); a top plate (110, 450, 710, 810) coupled along a front edge to a top edge of the front plate (115, 435, 750, 865) such that a channel is formed between the bottom (120, 430, 515, 620, 745, 855) and top (110, 450, 710, 810) plates; said channel being adapted to be partially or completely filled with concrete (400, 825); a vertical stopping plate (105, 455, 720, 815) coupled along a lower edge to a back edge of the top plate (110, 450, 710, 810); characterized by further comprising: at least one hat channel (125, 225, 425, 525, 740, 845) coupled to an inner surface of the channel, wherein the hat channel (125, 225, 425, 525, 740, 845) runs perpendicular to a length of the channel; and an embedding material (130, 230, 440, 850) inside the hat channel (125, 225, 425, 525, 740, 845), wherein the embedding material (130, 230, 440, 850) is adjacent to a bottom surface of the top plate (110, 450, 710, 810) so that a track may then be placed on top of the closure piece (100, 445, 520, 715, 860) against the vertical stopping plate (105, 455, 720, 815) and fastened to the closure piece (100, 445, 520, 715, 860) at the locations of the embedding material (130, 230, 440, 850). a bottom plate (120, 430, 515, 620, 745, 855); a front plate (115, 435, 750, 865) coupled along a bottom edge to a front edge of the bottom plate (120, 430, 515, 620, 745, 855); a top plate (110, 450, 710, 810) coupled along a front edge to a top edge of the front plate (115, 435, 750, 865) such that a channel is formed between the bottom (120, 430, 515, 620, 745, 855) and top (110, 450, 710, 810) plates; said channel being adapted to be partially or completely filled with concrete (400, 825); a vertical stopping plate (105, 455, 720, 815) coupled along a lower edge to a back edge of the top plate (110, 450, 710, 810); characterized by further comprising: at least one hat channel (125, 225, 425, 525, 740, 845) coupled to an inner surface of the channel, wherein the hat channel (125, 225, 425, 525, 740, 845) runs perpendicular to a length of the channel; and an embedding material (130, 230, 440, 850) inside the hat channel (125, 225, 425, 525, 740, 845), wherein the embedding material (130, 230, 440, 850) is adjacent to a bottom surface of the top plate (110, 450, 710, 810) so that a track may then be placed on top of the closure piece (100, 445, 520, 715, 860) against the vertical stopping plate (105, 455, 720, 815) and fastened to the closure piece (100, 445, 520, 715, 860) at the locations of the embedding material (130, 230, 440, 850). at least one hat channel (125, 225, 425, 525, 740, 845) coupled to an inner surface of the channel, wherein the hat channel (125, 225, 425, 525, 740, 845) runs perpendicular to a length of the channel; and an embedding material (130, 230, 440, 850) inside the hat channel (125, 225, 425, 525, 740, 845), wherein the embedding material (130, 230, 440, 850) is adjacent to a bottom surface of the top plate (110, 450, 710, 810) so that a track may then be placed on top of the closure piece (100, 445, 520, 715, 860) against the vertical stopping plate (105, 455, 720, 815) and fastened to the closure piece (100, 445, 520, 715, 860) at the locations of the embedding material (130, 230, 440, 850).