It all starts when two colossi find themselves within about a quarter-mile of each other. For this example, let's say our male lead character Leon Adler wants to depart one colossus - let's use Proteus - to a slightly taller colossus - we'll go with Triton.
All immigration is done by ropeway. Every colossus is fitted with several ballistae - medieval siege weapons that resemble sedan-sized crossbows - on the port and starboard sides of his/her back. These manned ballistae fire large grappling hooks, trailing over 1,000 feet of twin ropes, that land on the other colossus's back near its ballistae. I'm calling the firing/receiving areas "harbors" or "docking bays." So Proteus and Triton cross paths and Leon wants to go from Proteus back to his hometown of Triton, right? The ropeway is created when Proteus fires one grappling hook over to Triton and reels it back in until the ropeway has just enough slack for travel. Now that we have our ropeway we need to get our citizens across it.
Leon Adler and any other people wishing to travel to Triton have to traverse the ropeway, hand over hand, to their destination. Leon has with him a climbing harness that he straps into. The climbing harness is in the shape of a pair of boxer shorts but is mostly straps and butt support.
|Climbing harness, facing front.|
The trolley is modified with a simple cam device near its wheels. The cam device works similar to the hinge-mounted door stoppers you see at schools, retail stores and office buildings. When you nudge the door stopper down with your toe, it allows the door to be opened but it stubbornly brakes when anyone (or the door's weight itself) attempts to close the door. The cam device is virtually identical in terms of purpose and physics, only it's far smaller. Instead of a door, it's the trolley. Instead of the floor, it's the ropeway. Now, these cams really do exist and are a different part of rope-climbing rigs, but we'll get back to that. With a cam that only allows the trolley (and its rider, Leon) to move in one direction, Leon can climb the rope to the higher point (Triton) freely without risking sliding all the way back down to Proteus's ballista. The cam stops them from losing ground.
In addition, there are two other pieces of climbing gear attached to our intrepid detective to aid in his journey. These are two different types of foot ascenders. The first is a basic foot ascender: a set of nylon straps that tie around the shoe with an all-important cam device near his ankle. When Leon is ready to start his journey, he threads the cam on his foot through the ropeway and closes the lid on the outside of the cam so it doesn't slip out. Now he can, for all intents and purposes, climb up the ropeway with this foot, using the cam and his body weight like rungs on a ladder.
|Foot Ascender: Alone (top) and mounted to boot (bottom)|