I picked up several "Y" style hangers from the local hardware store (Home Depot carrys em..$9.99 each)
mounted two push plates (6x6x 1") to the end of a cut to fit 2x4 and installed th
e Y brackets spacing each so the upper bike wouldn't interfer with the lower and both were off the floor.
Have a friend who did something simila
r using two sets of the 2x4 trees with the Y which allowed him to place 4 bikes in the center of an unused hallway and have easy access to each.
