Occurrence

When I open my table in Surfaces>Create Grid, I cannot select some of my fields to grid.

Solution

The create grid tool only supports numeric fields types for gridding.
If you have numerical data in a Char field, you will need to change this under Table>Maintenance>Structure into a numeric field type, such as Float.

Note: if you character field contains any character entries such a '<0.05' or 'BDL', these will be lost upon conversion to a numeric field. Use Discover's Data Utilities>Select by Group to evaluate the contents of your character fields prior to conversion, and if necessary the Data Utilities>Text Search and Replace tool.