At my undergrad there is a small archway that leads from the campus to Main Street where some of the houses are that you aren't supposed to walk through until you graduate. I don't really know why actually. It might be bad luck or it could have been some tradition from back in the day. All I know is that it is pretty hard thing to remember not to walk though when you have been drinking a few beverages.
As for seals in sidewalks I have never seen that. The only thing that I have seen is letters that were put into the concrete sidewalk.