which extends substantially perpendicularly relative to the longitudinal direction of the channels 22 a portion 34 i e a receiving portion which is of a size which complements those of the female inner shape 15 of a tool head 14 of the set of tools defines a step of the bar 32 each portion 34 is spaced from the base 20 and transversely retains the fork 14 relative to the bar 32 a step of the bar 32 is arranged substantially in the same plane as the associated housing 22 of the handle 18 of the corresponding tool 12 and the bar 32 has cross sections which increase progressively from one portion 34 to the following portion a protruding tongue 36 extends the stepped bar 32 in the longitudinal direction of the channels 22 a mark 37 which is integral with the tongue 36 is arranged facing each portion 34 of the stepped bar 32 each mark 37 indicates the opening dimension of the female inner profile 15 of the head 14 of the tool 12 the base 20 further comprises a tapered end 38 which is directed towards the bar 32 and spaced therefrom by a space 39 for receiving the tool head 14 as will be described below the hollow bar 32 opens in each of the lateral walls 26 and 28 respectively in the region of holes 40 and 42 fig4 respectively a metal clamp 44 fig4 which is positioned between two ribs 45 of the rear face of the base 20 fig2 is fitted and fixed by a fixing element not illustrated which is itself screwed into a blind hole 46 the clamp.