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Before proceeding, inspect the exposed risers for any looseness. If a riser is loose or not tight against the skirt board, use a hammer to gently tap the riser outwards from behind until it's snug against the skirt board. To secure it in place, insert a wooden shim into the gap behind the riser. Apply construction adhesive to the shim before driving it in to ensure a firm hold. Repeat this process for all accessible loose risers.