From: Mind Bluff on 11/10/2005 (S459)
Source: http://mindbluff.com/foursq.htm

Here is the Answer:

First: slide the second top horizontal stick in the upper 

row horizontally to the right (its own length in 

distance). Second: place the second horizontal bottom 

stick (in the lower row) so that it is now perpendicular 

to the stick you just moved.  See picture above.