A steerable device comprising: a tubular sheath (10, 110, 210, 310) comprising: a proximal end (110 P, 210 P, 310 P); a distal end (110 D, 210 D, 310 D) opposite the proximal end; and at least one reconfigurable section disposed intermediate the proximal and distal ends and possessive of an increased flexibility, the at least one reconfigurable section comprising at least one helical slot (12, 112, 212, 312) formed through the wall (14, 114, 214, 314) thereof, the at least one helical slot (12, 112, 212, 312) defining: a pitch along the axial dimension of the tubular sheath (10, 110,210, 310); and a pattern with a periodically-varying width along a length axis of the tubular sheath (10, 110, 210, 310); and an elongate control element (120, 220, 320) defining a proximal end and a distal end, the control element (120, 220, 320) attached to at least one part of the tubular sheath (10, 110, 210, 310) in order to enable an operator to vary the length of the tubular sheath by imposing a force to the control element (120, 220, 320) that also causes a relative tangential rotation between adjacent wall sections (14, 114, 214, 314) that define the slot (12, 112, 212, 312), resulting in a known, limited, controllable torsional rotation of the distal end of the tubular sheath (110 D, 210 D, 310 D) without torsional rotation of the proximal end of the tubular sheath (110 P, 210 P, 310 P). a tubular sheath (10, 110, 210, 310) comprising: a proximal end (110 P, 210 P, 310 P); a distal end (110 D, 210 D, 310 D) opposite the proximal end; and at least one reconfigurable section disposed intermediate the proximal and distal ends and possessive of an increased flexibility, the at least one reconfigurable section comprising at least one helical slot (12, 112, 212, 312) formed through the wall (14, 114, 214, 314) thereof, the at least one helical slot (12, 112, 212, 312) defining: a pitch along the axial dimension of the tubular sheath (10, 110,210, 310); and a pattern with a periodically-varying width along a length axis of the tubular sheath (10, 110, 210, 310); and a proximal end (110 P, 210 P, 310 P); a distal end (110 D, 210 D, 310 D) opposite the proximal end; and at least one reconfigurable section disposed intermediate the proximal and distal ends and possessive of an increased flexibility, the at least one reconfigurable section comprising at least one helical slot (12, 112, 212, 312) formed through the wall (14, 114, 214, 314) thereof, the at least one helical slot (12, 112, 212, 312) defining: a pitch along the axial dimension of the tubular sheath (10, 110,210, 310); and a pattern with a periodically-varying width along a length axis of the tubular sheath (10, 110, 210, 310); and a pitch along the axial dimension of the tubular sheath (10, 110,210, 310); and a pattern with a periodically-varying width along a length axis of the tubular sheath (10, 110, 210, 310); and an elongate control element (120, 220, 320) defining a proximal end and a distal end, the control element (120, 220, 320) attached to at least one part of the tubular sheath (10, 110, 210, 310) in order to enable an operator to vary the length of the tubular sheath by imposing a force to the control element (120, 220, 320) that also causes a relative tangential rotation between adjacent wall sections (14, 114, 214, 314) that define the slot (12, 112, 212, 312), resulting in a known, limited, controllable torsional rotation of the distal end of the tubular sheath (110 D, 210 D, 310 D) without torsional rotation of the proximal end of the tubular sheath (110 P, 210 P, 310 P).