How do I get my father to stop waking up at night and peeing in the closet? Clothes pins?  

Take Dad to a doctor. A person concerned about his father's nighttime urination in the closet should take dad to see a primary care doctor and a urologist. Possible issues include: does dad get a full bladder several times at night due to blockage; is the blockage a big prostate or prostate cancer; does dad have some dementia and doesn't know where the toilet is; plus what other medical conditions going on?