Minecraft wiki entry for Transmission, associated text: Transparent blocks that support redstone dust do not "cut" redstone dust, so "ladders" of these blocks can be made zig-zagging back and forth upward. Glowstone and upside-down slabs are the most commonly used supporting blocks, but upside-down stairs, glass, and hoppers also can be used. Redstone ladders are 2×2 alternating tileable for short runs, or 1×4 alternating tileable with repeaters.