Yoga Bolsters are used to support the body allowing you to relax and stretch without straining. Asanas where bolsters are particularly useful include Adhomukha Virasana (Downward facing hero pose), Supta Baddhakonasana (Reclining bound ankle pose), Viparita Karani (Inverted lake pose) and Viparita Dandasana (inverted staff pose). However they can be used in conjunction with other props to provide elevation, cushioning or support in many other asanas.
Sand bags are used to deepen postures and to assist in stretching.