This is a pop-up rig made of Braid and a 'Depth Charge' weight, although a single shot would do the job. The positioning of the shot determines the height of the popped-up, buoyant, bait from the lake bed.
Added by Julian Grattidge;
A pop-up rig allows the angler to position a bait up off the lake bed. There are a number of scenarios where you may find it beneficial to do this, but in the main it is to do with positioning the bait above any weed that may be present or general detritus that could mask a bottom bait like leaves or silt.
That said, it has become common practice for many anglers to use a pop-up approach where there is no actual need for it to be popped up, i.e. a clean hard bottomed lake. The feeling in such situations is that it just offers something a little different to the norm which may get a result. Personally I only fish pop-ups where absolutely necessary, much preferring a critically balanced approach wherever possible as I believe it offers a more natural presentation. However, I have many angling companions who fish pop-ups as part of their standard approach and often take good numbers of fish.
A top Tip would be to try using pop-ups in Winter, where there is often a lot of leaf litter on the lake bed which allows the bait to sit just above all the decaying vegetation and hopefully, right under the nose of any passing carp!