Review on Swanson CCL001 Cross Check Tool by Marvin Short

Ordered received 2. Easy to read. Tested on a previously known flat surface by rotating in 90 degree increments. The bubbles were slightly off-center. I felt around the bottom edge of the plastic case, scraping off tiny ridges with my thumbnail. (Do not use a knife as this can result in an uneven surface.) Both bubbles were then centered and stayed that way when inverted. First used on a portable telescopic tripod. Fits perfectly! Attachment with 2 pieces of double-sided adhesive tape. (Ultimately you can drill and cut 2 small screw holes.) Be careful not to overlap the tape as this will create a burr that will prevent the case from being flat. Storage of the 2nd for a future, still defined need.