Does your lower back bother you during savasana (corpse) pose? Slip a foam roller under your knees to help relieve some pressure [as shown].
Need help holding extended triangle pose? Use a short roller (a little taller than most yoga blocks) to help you balance [as shown].
Foam rollers can be used in a variety of different yoga poses and postures and may help you balance or release your muscles more easily than a yoga block.