# Regex Model

Regex models provide a flexible control for defining the exact format of the strings that you are interested in by allowing you to define the characters you want to find via a regular expression.

To use a regex model, after adding the tool, configuring the ROI and setting the character Feature Size, process the tool (press the Book icon). Then create your regex model (from the Tool menu, select Edit Models).

The regex model will return the characters that match your regular expression, within the ROI that lie along a single horizontal line, which is defined by using the Angle parameter, and is the allowable deviation from horizontal.

When constructing your regular expression, the simplest wildcard is the period; it means "match any single character." You can then use modifiers after characters or wildcards to specify how many characters to match.

Note: The minimum match length for the regex model is three characters (not including the space character) or longer.