1. A guide tube assembly through which an endoscope is to be inserted with the guide tube assembly and endoscope to be inserted into a body said guide tube assembly comprising: a porous tube of a tubular shape formed of a material capable of being stretched axially without deformation of said tubular shape and capable of being bent without deforming said tubular shape, said tube having a forward end, a body comprising separable wound sections would around said porous tube, said separable wound sections axially movable along said porous tube, said separable wound sections being drawn together toward said forward end when said porous tube is stretched axially in a configuration to form a stiff body conforming to the configuration of the porous tube to fix the guide tube assembly in said configuration, said separable wound sections normally being separated from each other to enable said body to be flexible to be able to assume said configuration.