Clamp for inserting a flexurally elastic strand through an orifice of a receptacle, the clamp comprising a longitudinal housing which is able to accommodate a segment of the strand and in which the strand can slide, the clamp (1, 1b) comprising: • a blocking means (3, 3c) comprising a first part of the housing, • a guide means comprising a second part of the housing, the guide means being configured to at least partially surround a second part of the accommodated segment and configured to guide the clamp in the direction of the orifice of the receptacle, in which clamp the blocking means (3, 3c) is able to flexurally deform a first part of the accommodated segment when an external pressure is applied to the blocking means, which is intended to be used with the strand of which the elastic force returns the first part of the segment to its initial shape when the external pressure is no longer applied, the strand being prevented from sliding by the flexural deformation of the first part of the accommodated segment, and said blocking means (3, 3c) further comprises: • a lower jaw (3a, 3d) which is fixed and secured to the guide means with which it forms a single piece, comprising the first part of the housing, and • an upper jaw (3b, 3e) which is movable with respect to the rest of the clamp, able to be guided towards the lower jaw (3a, 3d) and to at least partially enter the first part of the housing in order to cover the first part of the accommodated segment, the upper jaw (3b, 3e) having a nonrectilinear profile so as to impress a nonrectilinear shape on the first part of the accommodated segment when the jaws ((3a, 3b), (3d, 3e)) are moved together, in which clamp lower contact points are disposed on the lower jaw (3a, 3d) and upper contact points are disposed on the upper jaw (3b, 3e), said contact points being configured to be disposed alternately under and over the first part of the accommodated segment in order to apply a pressure to the bottom and top of said first part of the accommodated segment, and in which clamp the jaws ((3a, 3b), (3e, 3d)) are configured to move apart from one another when said external pressure is no longer applied, the upper jaw (3b, 3e) being able to be pushed away from the lower jaw (3a, 3d) by an elastic force of the strand returning to its rectilinear shape. • a blocking means (3, 3c) comprising a first part of the housing, • a guide means comprising a second part of the housing, the guide means being configured to at least partially surround a second part of the accommodated segment and configured to guide the clamp in the direction of the orifice of the receptacle, in which clamp the blocking means (3, 3c) is able to flexurally deform a first part of the accommodated segment when an external pressure is applied to the blocking means, which is intended to be used with the strand of which the elastic force returns the first part of the segment to its initial shape when the external pressure is no longer applied, the strand being prevented from sliding by the flexural deformation of the first part of the accommodated segment, and said blocking means (3, 3c) further comprises: • a lower jaw (3a, 3d) which is fixed and secured to the guide means with which it forms a single piece, comprising the first part of the housing, and • an upper jaw (3b, 3e) which is movable with respect to the rest of the clamp, able to be guided towards the lower jaw (3a, 3d) and to at least partially enter the first part of the housing in order to cover the first part of the accommodated segment, the upper jaw (3b, 3e) having a nonrectilinear profile so as to impress a nonrectilinear shape on the first part of the accommodated segment when the jaws ((3a, 3b), (3d, 3e)) are moved together, • a lower jaw (3a, 3d) which is fixed and secured to the guide means with which it forms a single piece, comprising the first part of the housing, and • an upper jaw (3b, 3e) which is movable with respect to the rest of the clamp, able to be guided towards the lower jaw (3a, 3d) and to at least partially enter the first part of the housing in order to cover the first part of the accommodated segment, the upper jaw (3b, 3e) having a nonrectilinear profile so as to impress a nonrectilinear shape on the first part of the accommodated segment when the jaws ((3a, 3b), (3d, 3e)) are moved together, in which clamp lower contact points are disposed on the lower jaw (3a, 3d) and upper contact points are disposed on the upper jaw (3b, 3e), said contact points being configured to be disposed alternately under and over the first part of the accommodated segment in order to apply a pressure to the bottom and top of said first part of the accommodated segment, and in which clamp the jaws ((3a, 3b), (3e, 3d)) are configured to move apart from one another when said external pressure is no longer applied, the upper jaw (3b, 3e) being able to be pushed away from the lower jaw (3a, 3d) by an elastic force of the strand returning to its rectilinear shape.