Abstract: The disclosure relates to electronic units formed by two printed circuit type boards that are electrically and mechanically coupled and that have a single plug for their connection. To facilitate the placing of these units between two pairs of grooves, the assembling the two boards comprise adjusting elements to adjust the distance between the two boards to two distinct values: one when the boards are inserted into the grooves and the other for an effect of locking the boards between the pairs of grooves. To this end, it is possible to use bars crossed by a screw that makes it possible, by screwing, to place two outside sections of the bar in a position of overthrust with respect to an inside section of the bar. The screwing is done after the electronic unit has been inserted into the grooves in order to lock the boards against the flanks of the grooves.