Sectional modular gutter for forming drainage channels with a grid for pedestrian and/or vehicular traffic, comprising a gutter module provided at one end with a male joint and at the other end with a female joint, the joints being of the guillotine type, the gutter module being provided on the outer lateral surface of its body with transverse ribs extending in planes perpendicular to the longitudinal axis of the gutter, the transverse ribs being grouped in pair of ribs repeated at equal distances along the body, the distances being submultiples of the total length of the gutter module, in such a way that, when the gutter module is cut transversely, in the small space between the two ribs of one of said pairs of ribs, the resulting module portion having the female joint at one end terminates at its other end produced by the cut in a male joint, allowing a plurality of such gutter modules, either complete or shortened, to be connected in succession and form a drainage channel having a desired length on any occasion, characterized in that: (a) the male joint is formed by two or more transverse ribs and the female joint is formed by corresponding grooves and in that each of said groups of transverse ribs is formed by at least four or more transverse ribs, in such a way that, when the gutter module is cut in the median part of one of these groups, the resulting module portion having the female joint at one end is provided at its other end produced by the cut with ribs reproducing the male joint, in such a way that a plurality of such gutter modules, either complete or shortened, can be connected to each other by connecting the grooves of the female joints to the ribs of a male joints, so as to form joints of the labyrinth type which are substantially sinusoidal, intrinsically highly watertight and can be easily sealed with a small amount of added material, of the silicone type for example, or even without such added material; (b) the gutter module has the shape of a channel and has L-shaped longitudinal retaining edges to contain the grid for pedestrian or vehicular traffic, the outer surface of the body of the gutter module being further provided with transverse fins formed in one piece with the body and extending in planes perpendicular to the longitudinal axis of the gutter, the fins having a U-shaped outline in frontal view of the gutter module which, except for the greater dimensions, substantially reproduces the internal shape of the body, the ends of the fins being in contact with the bases of the said retaining edges without projecting beyond them, and one of said transverse fins being set back by a precise amount from one end of the gutter module, wherein the portion body which is located between this one fin and the end of the gutter module has two of the transverse ribs made in one piece with the body and terminating at the bases of said edges, to form the mate joint of the gutter module, wherein the first of said two transverse ribs of the male joint is substantially flush with or slightly set back from the end of the gutter module, while the other, inner, rib is separated from said first rib by a first distance substantially equal to the thickness of one of said ribs, while the distance between the inner rib and the neighbouring fin is equal to or slightly greater than said first distance. (a) the male joint is formed by two or more transverse ribs and the female joint is formed by corresponding grooves and in that each of said groups of transverse ribs is formed by at least four or more transverse ribs, in such a way that, when the gutter module is cut in the median part of one of these groups, the resulting module portion having the female joint at one end is provided at its other end produced by the cut with ribs reproducing the male joint, in such a way that a plurality of such gutter modules, either complete or shortened, can be connected to each other by connecting the grooves of the female joints to the ribs of a male joints, so as to form joints of the labyrinth type which are substantially sinusoidal, intrinsically highly watertight and can be easily sealed with a small amount of added material, of the silicone type for example, or even without such added material; (b) the gutter module has the shape of a channel and has L-shaped longitudinal retaining edges to contain the grid for pedestrian or vehicular traffic, the outer surface of the body of the gutter module being further provided with transverse fins formed in one piece with the body and extending in planes perpendicular to the longitudinal axis of the gutter, the fins having a U-shaped outline in frontal view of the gutter module which, except for the greater dimensions, substantially reproduces the internal shape of the body, the ends of the fins being in contact with the bases of the said retaining edges without projecting beyond them, and one of said transverse fins being set back by a precise amount from one end of the gutter module, wherein the portion body which is located between this one fin and the end of the gutter module has two of the transverse ribs made in one piece with the body and terminating at the bases of said edges, to form the mate joint of the gutter module, wherein the first of said two transverse ribs of the male joint is substantially flush with or slightly set back from the end of the gutter module, while the other, inner, rib is separated from said first rib by a first distance substantially equal to the thickness of one of said ribs, while the distance between the inner rib and the neighbouring fin is equal to or slightly greater than said first distance.