A pull-through is a length of strong, rot proof string, inserted into a wall cavity, conduit, pipe or tube to enable wires and cables to be easily drawn from one place to another.
I would like to offer a piece of advice that will save you a lot of heartache and frustration. Whenever you install anything that needs connecting to other places around the home or beyond put in a nylon pull-through cord alongside whatever you are puting in, make the pull-through two and a half times the length of the cable run, tied off at each end.
If the first cable that will be going into the tube is stiff, tie the string to the end of the cable so that it goes through at the same time. If the conduit is being installed for later use or the first cable will not "push" in without kinking and jamming, tie the end of the string to a wad of cotton wool or something similar to make a lightweight piston, push it into the conduit a ways and push some spare string in after it, then use it like a blowpipe, either by mouth or use compressed air blow the wad along the tube taking the string with it.
With this forethought I was recently able to run 30 metres of network cable from the house (picture 2), through an underground conduit to the tool shed (picture 3), then through another underground conduit to my home office (picture 4), a conduit that was originally installed to run a cable TV feed.
The remainder of this instructable is more of a case study than a project for anyone to emulate but it reinforces my message on pull-throughs.
Step 1: Ugly Fireplace Is Now Hidden Entertainment Centre
My home when first purchased was not the most modern place I have lived in, amongst many other things that needed attention was the recessed fireplace with fitted back boiler gas fire which was, to be frank, horrible!
Step 2: Getting Rid of the Fire
This setup was a complete waste of space as the back boiler and its flue were all that were in an enormous full height full width cupboard that intruded into the kitchen beyond, the photo's show cupboard in the process of being disassembled and the re-routed flue.
A new modern boiler in the airing cupboard allowed me to remove the gas fire, reroute the flue and extend my kitchen into the previously dead space.
Back round the other side of the wall I now had the means and the space to hide my set top boxes, HDMI splitters and antenna distribution amplifiers, all of which, with the attendant spaghetti of wires, looked so messy.
At this stage I ran 2 conduits under the floor to the office and another room, each with a pull-through.
Step 3: Old Fireplace Out
The horrible stone mantle and the firebrick base were removed, insulation foam was installed and a new wooden floor fitted. In the photo's can be seen the back of the kitchen cupboards with some very usable space below and behind them. I then clad the walls in good quality plywood to cover the flimsy hardboard wall finish. there is a pull-through attached just inside the square hole in the back panel, the other end is attached to the back of a kitchen base unit, it will later be used to run 2 HDMI and one coax cable....with ease :)
Step 4: Install Flat Screen and Feature Fire.
Once the ply panelling was up, I installed a multi socket to power all my kit, put up the brackets for TV and fire then papered and painted the alcove before final installation.
The white frame under the fire hides all the boxes and cables that connect up all around the building. The last picture shows George inspecting the smoked plastic cover fitted into the lower frame that hides everything but still allows use of remote controls for all the tech, there are a couple of IR repeaters that allow remote controls to be used from anywhere in the building.
The pull-throughs made running all the cables a doddle.