Materials: 1. Kallax 77x77cm 30 3/8×30 3/8″ black-brown. 2. Kallax Insert with door black-brown. 3. KNIPSA Basket seagrass It’s not too difficult to build, but cutting out the hole between the two top shelves took a bit of time measuring out. The door actually has its own four walls, so when cutting out the hole, you have to cut both through the inner wall of the shelf plus the wall of the “insert with door”. The scratching mat on the left side is made out of a wall-to-wall carpet which we just glued on. On the right side of the shelf we tightened a sisal rope which we also glued. Inside we used some more of the carpet to make it more comfy. In the two bottom shelves we put two KNIPSA baskets for storing his toys and also our own things. We got the inspiration for this scratching furniture here on IKEA hackers. Mostly from these two hacks: Expedit scratch post and cat activity center.