There’s a common rock climbing maneuver — the technical name of which, if there is one, escapes me — that involves moving up or down in a narrow space by bracing one’s back against one wall and hands and feet against the opposite wall. My feline friend here will demonstrate:
See? That’s how it’s done.
Please note: Professional stunt climber on closed course. Do not attempt this at home. Always use a safety rope and harness when climbing. Do not attempt this maneuver in an inverted position.