Well I think he meant "closing" an open gap, which essentially means filling an open gap.
There is a theory that all gaps are closed (or filled) at some point or other. But I seriously disagree on this. Gaps are useful for trading but it is not necessary for them to close out. In some cases they do and in some cases they don't. There is no hard and fast rule on that.
E.g. There is a weekly gap on levels of 950 on the NIFTY. Now, since all gaps have to be closed (which is what is proposed my many technicians) then at some time or other NIFTY will return at 950 levels.
:lol: I seriously doubt this. May be 2012 will lead it there ...