The type of pipe your reference shows is flexible, Dave. The very fact that it is flexible implies that it can be inserted or introduced in, for example, twisted, winding or coiled containing or enclosing structures, e.g. conduit or ducts, or pushed through a hole or orifice, as lipabel says. I think that's what the author is getting at here. 'Hose pipe', 'hose piping' or simply 'hose' might be a more appropriate term for the material shown in your reference, by the way (see
http://www.1911encyclopedia.org/Hose-Pipe ). That would be more in keeping with the Dutch term 'slang' too, which implies flexibility.