First you need to determine if the closer is handed. A handed door closer will only have a single shaft on one side of the closer for the arm to attach to.
If the closer is handed then to determine the handing of the closer, look at the top of the closer where the arm attaches to the spindle/pinion. On either side of the spindle/pinion, casted into the cylinder body, you will see an RH and a LH. If the three regulation valves (Backcheck, Main Speed, and Latch Speed) are on the side with the RH, it is a Right Hand closer. If the three regulation valves (Backcheck, Main Speed, and Latch Speed) are on the side with the LH, it is a Left Hand closer.
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