Magic Tricks

Remember, Solo, as shown, is a two stage trick.
The first stage is the 'disappearance' of the chosen signed card between the Kings. A great effect on its own that can be used in many other ways which are discussed on the DVD ;-)
The second stage is the 'appearance' of the signed card in the card box. Another great effect!
Generally, when asked about the gimmick, most are asking about the first stage.
Thus, the gimmick is not really fragile. It'll hold up throughout many uses. The technique/materials used aren't anything new and are readily available. Mark doesn't teach you how to make the gimmick. However, once you see it, as with a lot of gimmicks in magic, you'll be able to reproduce one very easily.
And, no, it is not difficult to make.
Best wishes...