# Blue Read Tool – String Model

The string model is the simplest model to use and define; you simply define the minimum number of characters you expect to find, along with the angular variation of the characters from the horizontal boundary of the ROI that you expect to encounter in your images.

To use a string model, do the following:

1. After adding the tool, configuring the ROI and setting the character Feature Size, process the tool (press the Book icon).

2. To create your string model, from the Tool menu, select Edit Models, and from the Model Editor dialog, select String Model.

3. Enter the number of characters the string should contain in the Minimum Length field.
4. The tool will return the specified number of characters that are present in the ROI. The matched characters must lie along a single horizontal line, which is defined by using the Angle parameter, and is the allowable deviation from the horizontal axis of the ROI.
5. Close the dialog by pressing the X button in the top-right corner of the dialog.
6. The model will then be applied to the view that was open when the Model Editor was launched.
7. Process the tool (press the Book icon) to apply the model to the rest of the views.
8. Review the results. For more information, refer to the Working with Labels and Models topic.

### String Model Score

For Blue Read tool, a model score (model match score) is a combination of two things:

- The average score of the features in this model

- The "geometry score" based on the geometrical arrangement of the features in this model

As the geometrical arrangement is included in the calculation of the overall model match score, the model score could be less than 100% even when all the features have a perfect score of 100%, given that the geometry score is less than 100%.

For the string model, the "geometry score" is based on a combination of:

- how close the feature positions are to lying on a single line

- how equally the characters are spaced

For example, with a string model, given 3 features of score 100%, the overall match score will be slightly less than 100% as the geometry score of this model is less than 100%. The geometry score will always be less than 100% unless all the features are exactly collinear and exactly equally spaced.