I was searching the web for pictures or an explanation of how these gubbins work, but since google image search kept bringing up all sorts of gay porn "cock in hand" pictures, i figured this might be quite useful for some other noobs, so you are spared of the ordeal of searching for "tug nuts" on t'interweb...

These are the instructions that came with the MKS chain tugs I picked up from hubjub. obviously these will be different from other makes but it does show how this chain tug fits to the track ends etc. Its also nice and descriptive :P

Hope someone finds it useful.