The range is not level.
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Level the range, referring to the illustration:
Use a 3/8" (10 mm) open-ended wrench to adjust the right and left rear adjustments (2).
To adjust the right and left front adjustments (3), hold the locknut with a 5/8" (16 mm) open-ended wrench while turning the adjustable nut with a 1/2" (13 mm) open-ended wrench.
Check with a spirit (bubble) level and readjust as necessary.
Slide the locking clamp (1) back.