Simpsons Treehouse of Horrors GitD Sign These are about 1/3" thick making them able to free stand. The "Thin" option is 1/5" thick and designed to stick to a wall/shelving or lean them up against something. Great for displaying with your collectibles like Funko Pops! These are display signs made of glow in the dark plastic. They are normally White and glow Green in the dark after absorbing light Black lights are amazing at getting these to glow. Sunlight is also good. Normal lights also work Homer Bart Marge Lisa Krusty