One board, a lot of uses
Calf and Achilles stretches
Heels low, hands on the wall, lean in. A deeper, steadier stretch than a stair edge.
Heel-elevated squats
Raise your heels to squat deeper and stay upright. Great for knees-over-toes training.
Desk footrest
Set it low and rest your feet on it while you work. Slides under any desk.