Run rigs are a method of utilising the lead where the line runs freely through the swivel or bead connecting it to the mainline. The advantage of this type of lead usage is that it creates instant pressure on the bobbins and alarms when the bait is picked up as there is no obstruction point between the hook and the rod.
Here are some links to useful articles about run rigs on external webpages:
Watch videos about run rigs-
The Keith Moors run rig
Total Carp running rig
Brian Wingard’s carp run rig