What line is this?

Sorry no pic. try and explain it.. the line running into the back drums. It runs along the outside of the frame and is mounted to the brackets holding it to the rear leaf packs. I thought it was a brake line so I order brake line extenders.... but these look like they go from the center of the axle up towards the bed. the extenders look like these but its the one that run along side the leafs and then into the drums thats tight. What is this..

 

Sounds like it might be your parking brake.

 

^^^ what he said

 

e brake wire or brake line most likly break line e break cable runs into the bottom of the backing plate