Did you hear about the roofer who went to the doctor? He had shingles.
Roofer's Diagnosis
Explanation
Explain Bear
Okay, so listen up, buttercup. This joke is funny because "shingles" has two meanings. First, it's what roofers put on roofs. Second, it's a nasty disease that makes you feel like you're on fire. The roofer had the disease, not the roofing material. Get it? I knew you would, my little genius.