The lines are tab leaders. To display the Tabs dialog box and look at the settings, you can double-click the tab indicator (the backward "L") on the horizontal ruler. For more on tabs, see http://word.mvps.org/faqs/formatting/SettingTabs.htm.

Note, however, that you may find it easier to design a form using table cells (add and remove borders appropriately). For more, see http://word.mvps.org/FAQs/TblsFldsFms/LinesInForms.htm (you can ignore the links to articles on creating protected forms).

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional