If you are planning a garden terrace, a driveway border, or need to secure a slight slope, you have probably come across the term Keilbohlen (wedge boards). But what exactly are they, and how do you use them correctly? This post covers the most important applications, step-by-step installation, and common mistakes to avoid. What Are Keilbohlen? Keilbohlen are tapered, profiled wooden boards (usually made from pressure-treated softwood or oak) that interlock vertically to form a retaining wall. Their wedge shape allows them to be driven into the ground, creating a stable barrier against soil pressure.