CHANNEL-POSITIONING MACHINE, being the type used in the placing and alignment of the prefabricated and dovetailed small troughs and which are provided with a loading platform, a feeding train, an aligning box and a rotating conveyor,for the small troughs with an enlarged section configuration in "U" shape and the ones also having coupling and linking means to the tractor "T", being essentially characterized, in that: - the loading platform has a framework with wheels, which is perpendicularly journalled to the feeding train by means of hydraulic cylinders; - the feeding train is formed by three sections of foldable frameworks among them, a first section, another central section and a third section, having rolling means for the small troughs, based on parallel axis with wheels with rubber profile, receiving the axis the driving action by means of a transmission by chains and the axis of each section, and receive independently the driving action from one another, in order to have different speed in each section, and of the axis and wheels; - the aligning box which has a long configuration with section in "U" shape, and has in the upper part a swiveling platform, opposite to the outlet of the third section of the feeding train, under such swiveling platform, the bottom of the aligning box has a ramp and two wheels in the end of an axis driven by a chain while in the central area and in the opposite end of the swiveling platform, two towing means are provided for the small troughs, which are formed each one of them by two pairs of vertical rollers driven by the upper means and which are susceptible of being displaced towards the outer part until contacting with the internal areas of the small troughs walls, also having the aligning box in its external wall few stops in opposition to the hydraulic cylinder of the third section of the feeding train, while in its front end it is provided with the framework with the guiding means on the trench; - the rotating conveyor is formed by a rotating post on the housing in solidarity with the central section of the feeding train and next to the framework of the loading platform which post has in the lower part rotating means and exhibits in the upper part coupling sections with two telescopic frames, a lower one and another upper one with regulation means between them based on a hydraulic cylinder and a chain pulley, also having an upper frame of some coupling means with a pressure jaw in horizontal position and forming a 45° angle in relation to the upper frame and the rest of the set of the rotating conveyor 4; further characterized in that it comprises: - a conveyor for the supply of small troughs rows up to the feeding train; - a positioning device of the covers on the small troughs already installed on the trench, based on one inclined platform and a framework coupled to the aligning box. - the loading platform has a framework with wheels, which is perpendicularly journalled to the feeding train by means of hydraulic cylinders; - the feeding train is formed by three sections of foldable frameworks among them, a first section, another central section and a third section, having rolling means for the small troughs, based on parallel axis with wheels with rubber profile, receiving the axis the driving action by means of a transmission by chains and the axis of each section, and receive independently the driving action from one another, in order to have different speed in each section, and of the axis and wheels; - the aligning box which has a long configuration with section in "U" shape, and has in the upper part a swiveling platform, opposite to the outlet of the third section of the feeding train, under such swiveling platform, the bottom of the aligning box has a ramp and two wheels in the end of an axis driven by a chain while in the central area and in the opposite end of the swiveling platform, two towing means are provided for the small troughs, which are formed each one of them by two pairs of vertical rollers driven by the upper means and which are susceptible of being displaced towards the outer part until contacting with the internal areas of the small troughs walls, also having the aligning box in its external wall few stops in opposition to the hydraulic cylinder of the third section of the feeding train, while in its front end it is provided with the framework with the guiding means on the trench; - the rotating conveyor is formed by a rotating post on the housing in solidarity with the central section of the feeding train and next to the framework of the loading platform which post has in the lower part rotating means and exhibits in the upper part coupling sections with two telescopic frames, a lower one and another upper one with regulation means between them based on a hydraulic cylinder and a chain pulley, also having an upper frame of some coupling means with a pressure jaw in horizontal position and forming a 45° angle in relation to the upper frame and the rest of the set of the rotating conveyor 4; - a conveyor for the supply of small troughs rows up to the feeding train; - a positioning device of the covers on the small troughs already installed on the trench, based on one inclined platform and a framework coupled to the aligning box.