Tracking a circuit path across a crack?
You can do a neater job, perhaps as robust perhaps not quite, by scraping the traces back 3-5mm from the crack on each side, exposing fresh copper, and bridging the crack with thin bare wires, perhaps 0.25mm diameter (AWG30). Get a nice round fillet of solder on each trace back some mm from the crack. If it isn't nice and rounded, you probably didn't scrape the solder mask off well enough, so clean the solder off with a wick or whatever and try again. 

You'll want to stabilize the board first, perhaps with some splints and epoxy on the component side. 

Board cracking is mostly a problem with cheap single-sided paper-based phenolic boards, which is fortunate because they're really easy to trace. Tracing circuits on multilayer boards is a bit more challenging.