Stand arms-length from wall, feet shoulder-width, squeeze shoulder blades back/down. Place hands on wall at shoulder height, slightly wider than shoulders. Keep straight body line head-to-heels; engage core. Bend elbows to lower chest to wall, feet planted. Push back to start.
Hands at shoulder height, ~1.5x shoulder-width apart, slightly inward. Body as one solid plank: feet to ears move together. Head aligned with spine (tongue on roof of mouth if neck strains). Engage abs to prevent sagging. Align ears-shoulders-hips-knees.