Design the Cat Tree
Design the cat tree and purchase 3/4-inch plywood, carpeting, PVC piping, and sisal rope to accommodate the dimensions of your project. Our measurements below may vary from yours, so adjust your plan accordingly.

Glue the Plywood Surface
Roll carpenter's glue onto the surface of one 3-foot-by-3-foot layer of plywood after cutting two base sections of those approximate proportions. Brush off any debris from the surfaces of both sections, and use a small paint roller and paint pan to facilitate applying the glue to such a large surface. Set the second plywood base on top of the first with the edges flush.

Drive in Screws
Drill countersunk shank holes about 8-inches off each corner and drive in screws to hold the two layers together more securely.

Add a Lip Around Base Perimeter
Add a lip around the perimeter of the base by screwing 3- to 4-inch wide lengths of plywood to the edges. Set these narrow strips on edge, butted against the raw edges of the base, and attach them flush with the bottom of the base. Overlap the corners rather than mitering them.

Draw a Circle
Set up a compass and pencil to span 3-inches in preparation for making the tower. A circle drawn with this compass setting (and the resulting hole cut) will be 6-inches in diameter. That is a good size for small to medium cats.

Cut Plywood
Cut the pieces of the tower from 3/4-inch plywood according to the plans. You will need four side panels that are about 3-feet by 18-inches. You will also need three panels that are about 17 1/4-inches square - two to form the ends of the tower and one for a center divider.

Mark Position for Center Divider
Draw a line across the middle of each side panel, to mark the position for the center divider and delineate an18-inch square on each end of the side panel. In each of those squares, draw diagonal lines from corner to corner so they cross at the exact center of each square.

Outline a 6-inch Circle
Place the compass point on the center/cross marks of each square and outline a 6-inch circle. You will have two circles marked on each panel, for a total of eight on the sides of the tower. Use the same method to mark a hold on the topmost end panel only.

Drill Starter holes
Drill a starter hole with a power drill just inside each circle drawn.

Cut out Nine Circles
Insert the jigsaw blade into the starter hole and then cut out each of the nine circles.

Glue Pieces Together
Glue together the sides, top, bottom, and center divider for the tower. Each side panel will overlap its neighboring panel on one edge and butt up against the flat surface of the opposite neighbor.  

Secure all Glue Joints
Use a pneumatic nail gun to secure all the glue joints for greater strength.

Staple Carpet
Drop a piece of carpet into the base (cut to fit) and staple it in place. Cut carpet to fit the side panels and the top panel exactly and staple the pieces in place.

Cut Carpet
Use a utility knife to cut from the center of the holes (now covered in carpet), back to the edges of the plywood circle. Make about six neat cuts, starting each time from the center of the hole so that you have pie-shaped pieces that are loose at the point and two sides, but still attached at the edge of the circle.

Apply Glue to Carpet
Apply glue to the underside of the carpet wedges.

Bend and Staple Carpet Points
Bend the carpet points to the interior of the tower and staple them to the plywood.

Obtain PVC Piping
Obtain four equal lengths of PVC piping about 5 1/2 to 6-feet long to serve as the superstructure for the gymnastic element of the cat tree. These will fit in the four corners of the base and meet above the center of the tower.

Glue Interior Surface of Pipes
Mix up some quick-setting epoxy glue and spread it on the interior surface of both ends of each of the four pipes after cutting eight 2-inch inserts of dowel rods that are the exact diameter of the interior of the pipe.

Slide Dowel into Wet Glue
Slide one dowel into the wet glue in each end of the four pipes so that the end of the dowel is flush with the end of the pipe like a plug.

Attach Sisal Roper to Exterior of Pipe
Attach a piece of sisal rope to the exterior of one end of the pipes only, screwing through the rope and pipe and into the wooden dowel. To stop the ends of the rope from fraying, neatly glue the fibers at the ends of the rope together, wrap the end with clear tape, and let them all dry before attaching the rope to the pipe.

Wind the Rope Tightly
Use your power drill to help wind the sisal rope tightly around the entire length of the pipe. First make a hole a little larger than the diameter of the PVC pipe in a block of wood and clamp the block so that it stands upright. The hole will be facing you and temporarily hold up the opposite end of the pipe. Drill into the wooden dowel plug at the end of the pipe with the sisal attached and leave the drill bit in the dowel. Now, use the drill to spin the pole while a second person guides the rope into place.

Knot the Rope
Knot the sisal rope at the other end of the pipe to hold the tightly wound spiral of rope covering in place.

Lean Knotted Rope Ends Inward
Put the end of the pipes with the screwed sisal in the four corners of the base and lean the knotted sisal ends inward until they meet like teepee poles above the tower.

Secure the Tops
Secure the tops by drilling laterally from one pipe into the next where they meet above the tower. Be sure to leave enough room to screw the next pipe in without bumping into the previous screw. Suspend a cat toy from the apex of the pipes.