Now that the floor is done, we can start building the frame. You will need to cut some 2"x2" boards first. Again, if your boards are not 1.5"x1.5", then you need to take your own measurements.
Cut six (6) 4' beams. Basically, cut three (3) of the 2"x2"x8' beams in half.
Cut two (2) 45" beams.
Cut four (4) 21" beams.
After cutting your beams, attach the first 21" beam to the center of two (2) 4' beams to form an "H" shape. Place a mark at 2' into each 4' beam, and that is where the screw show go. Screw the boards together using a 2.5" wood screw. When attaching two beams together like this, I like to stand on each beam on the ground while I screw them together to ensure a snug connection. Make sure the ground is flat if you try this.
The joint of the joined boards should look something like this.
Attach the two "H" sections to the floor assembly. It may be easier to do this with the floor and "H" frame on their sides.
When attaching the frame wall to the floor assembly, it is best to drill screws in from both directions. Make sure you offset the the screws (i.e. put one higher and one lower) so they do not hit each other on the way in.
Attach the two 4' beams to the top of the "H" frame walls using 2.5" screws.
Attach the two 21" beams to the top of each wall as shown in the picture, keeping the all the top beams flush with each other.
There is, unfortunately, not a picture for this step.
Install the two 45" beams on the side walls of the frames. These should be at the same level as the beams on the end walls so that a shelf can be placed on them. Attach these beams with 2.5" screws.
Decide which side of the cage will be the front. Measure 2' from the left side. This will be where the large bottom door goes. This door needs to be large enough to allow you to clean and put in or take out a litter box.
Measure the height from the floor to the bottom of the center wall beam. This should be approximately 19.5", but use your measurement for cutting the next beam. Cut a 2"x2" beam to fit in the space you just measured. Attach the beam with 2.5" screws, being sure that there is 2' of width between the beam and the left wall beam.