This instance is from Wikipedia and should be reused below a CC BY-SA license. They can be sculpted into many designs for the duration of this method, in some cases resulting in deep thumb-print like indentations on their own surfaces known as regmaglypts. From Wikipedia The ASL fingerspelling provided here https://edgarwhnps.total-blog.com/5-simple-techniques-for-sculpted-md-lakewood-61690188