Keeping the angles of a losange

[giobd]

When I create a losange, and I change the size vertically, the angles change:

How can I have this kind of losange, so that when I increase the size verticaly, the angle stay the same?
Thank you in advance!

[jmlevy · Accepted solution]

Select the 2 bottom points with the white arrow and pull them down, while holding down the shift key, to be sure that you actually move the points vertically.

[giobd]

Thank you! I don't why it didn't occur to me!