Free falling knockers are expendable. If the lure doesn't come free, you will have to break the line and lose both the retriever and the lure. Fortunately, used spark plugs are cheap. An alternative to the free falling knocker is the stringed knocker, which can be slowly lowered to the stuck lure on a rope or string. These knockers usually have a large side ring to attach the knocker to the line.
Some designs have hooks, chains or rings hanging off the bottom to help grab the snagged lure.
String retrievers require their users to spend time trying to get snagged lures back. Often, much more time than the tournament angler wants to spend. Therefore, you may not want to fool with the stringed knockers. Poles Pole retrievers can extend an anglers reach up to 12 feet or more Lures have a mystical tendency to get caught in rather awkward places. They may get stuck on stumps way back in the weed patch.