Joining two windows doesn't work [duplicate]

I click join area and then the Area Options dialog disappears and nothing happens.

marked as duplicate by Ray Mairlot, stacker, CoDEmanX, iKlsR♦Aug 13 '15 at 13:35

• Close the timeline first – VRM Aug 13 '15 at 2:00
• If you look at the system console, you will see an error printed: areas don't share edge. You can only join areas if the fully share an edge, but in your case the right-hand area shares an edge with two other areas. – CoDEmanX Aug 13 '15 at 13:32

quoting from the manual:

order to merge two window frames, they must be the same dimension in the direction you wish to merge. For example, if you want to combine two window frames that are side-by-side, they must be the same height. If the one on the left is not the same as the one on the right, you will not be able to combine them horizontally. This is so that the combined window space results in a rectangle. The same rule holds for joining two window frames that are stacked on top of one another; they must both have the same width. If the one above is split vertically, you must first merge those two, and then join the bottom one up to the upper one.