back leads

Question
in carp fishing,how do use back leads and what happeneds to then with a fish on?

Answer
I turly enjoy carp fishing also, even though in the U.S. they are considered "trash" fish and if caught are often thrown up on the shore and left for dead.  My personal largest was 43lbs.(19.6kg.) and I caught it on 6lb.(2.7kg.) monofilament on a splitshot rig with a #2 short shank O'Shaughnessy hook with a live Canadian Nightcrawler.  I sight casted to that beast, I could see him tailing, and he almost spooled me three times.  Well, back to the subject at hand.  Backleads are used so you don't spook schooling or free roaming fish.  The weight is put on so the line stays on the lake bottom and so the fish wont swim into the line an spook.  It is generally clipped onto the line after the cast, then by raising the rod tip,is slid down to the desired point.  When a fish is hooked the weight slides down to the fish.  I must say I would not use a large weight for fear of dislodging the hook from the carps mouth.  Here is a webpage that hass all you need to know, http://www.anglinglines.com/blog/a-quick-guide-to-using-backleads/