Always use them out of habit no matter the surface. Made mine out of two squares of plywood sandwiching a 2x6 board, put the plywood at opposing angles(grain wise) using the 2x6 in between. Have had these same blocks of wood for around 12 years. I use them under the wheel's too if necessary.
96 Vogue Prima Vista
The Kid's: Humphrie, the Mini Schnauzer and Georgie,wire haired dachshund.
Rainbow Bridge: Laddie,Scoutie,Katie,Cooper,Kodie,Rubie,Maggie, Cassie, Mollie, Elvis, Potter and Rosie Love You! (40+ years in all)