Calibration adjustments to my machinist level can be made after removing a round-sided access cover. The original access cover was very difficult to remove. I modified the original access cover and made a tool making it much easier to remove the cover. The cover already had a small groove around it’s perimeter that I enlarged to fit a standard 3/32” thick No. 115 O-ring. This provided a snug fit but yet easy to remove. I created a screw-on handle that fits into an existing brass thread insert installed on the face of the original cover. The threaded-end handle also served as a mandrel for holding the cover while machining the larger O-ring groove. The handle was made from 0.250” 2011-T3 aluminum rod and a clamp-type knurling tool produced the knurls. The clamp-type knurling tool is a better choice than the traditional plunge knurling tool when working with small diameter aluminum rod.