The ST-4 is the only rack designed specifically for the newer style STIHL BR 600 & 700 Series blowers with a black leaf grate on the bottom. Simply set your blower on the lower posts and pivot the top toward the rack, allowing the "sliding lip" to, slide under the handle. Complete installation by pulling the ball knob on the rack and lowering the "sliding lip" over the blower. The blower is secured at the top and bottom and will not move around.