I am not an expert on gaps, but here is some info on gap theory:
Price gaps are one of the most common technical signals. They also are one of the least understood. Here, we'll put gaps in their proper context and show how a classic theory can help you determine which gaps matter most.
While they are among the simplest technical conditions, price gaps - when successive price bars fail to overlap generate a lot of questions among traders. Why do gaps happen? How can we foresee gaps? Do gaps always get filled?