A guide for positioning an orthopaedic guide pin on a bone structure includes a base having an upper face, a lower face intended to bear against the bone structure, and a through-hole for the pin, said guide including several bearing members able to move in guide holes formed in the base, wherein each bearing member has a lower end facing the lower face and is able to be moved selectively between a retracted position inside the guide hole and at least one deployed position in which the bearing member protrudes from the lower face so as to have a salient lower end intended to bear against the bone structure in order to allow the base to be inclined.