The bathroom cupboard in our master bedroom was basically a waste of space so I added a shelf in it to use up the rest of the space. I went with the “assembly required” bookshelf motif for my shelf since I had a bunch of shelf clips left over from our bookcases. This meant drilling a teeny hole into the cupboard under the sink but not THROUGH it. To achieve this I set the torque on the drill at 8 and the speed at low. I also tied a string around the drill bit at the maximum distance that it could enter the wood.
I measured the length of the cupboard and cut it out of a pine board that I bought for $6.80. Now, if you use the clip in the above photo you will have to cut your board smaller than you measured in order to fit. I switched to plain ol’ straight bookshelf clips
Now I have an extra shelf that I will eventually put most of my makeup on.