This article is from the Baby Proofing FAQ, by Sandra Smith, email@example.com with numerous contributions by others.
From: firstname.lastname@example.org (Monica Fortner)
What we did was cover some sheets of 1/2 inch cork with clear contact
paper and then fasten that to the fireplace with Liquid Nails. The
cork was about the same color as our brick, so it looked ok. It has
held up for 3 years. My biggest concern is when we want to sell the
house, we may have trouble removing the Liquid Nail spots.