A chod rig is in essence a short stiff rig mounted on leadcore leader in the helicopter rig style.
It is best used in conjunction with pop ups, and utilised over silty and weedy lake bottoms.
Here are some links to useful articles about chod rigs on external webpages:
Watch videos about chod rigs-
Tying your own chod rig at Gardner Tacke
The chod rig in detail with Miles Gascoine
Adam Penning ties the Chod Rig
Rich Wilby explain the Chod Rig in detail