A sheath apparatus includes, a plurality of node rings configured to be tilted with respect to each other, each node ring defining a substantially cylindrical wall and having at least one hole passing through said cylindrical wall, the plurality of node rings being arranged next to each other along a linear axis such that consecutive node rings contact each other at a contact plane a manipulating wire going through the holes in said stacked node rings and a position restoring component configured to restore said stacked node rings from a tilted position to an original position, wherein said position restoring component is located inside or outside of the stacked node rings.
