Anxious to get the job done? Cutting corners by ordering prior to the completion of tiling is the single biggest error both contractors and do it yourselfers commit. This applies particularly to frameless enclosures.
Framed enclosures - within 1/4" accuracy
Frameless enclosures - within 1/16" accuracy
Note: To receive a free estimate this level of accuracy is not required.
Using a tape measure and level take complete and thorough measurements no matter how insignificant they seem. It is better to provide more information, rather than miss a measurement.
Door Opening Bottom 27"
Left Wall is Plumb
Right Wall is out of plumb 1/4"
Therefore: Width Measurement at Top must be 27¼"