What are "closure strips"?
Closure strips match the corrugation pattern of the panels of Suntuf, Palruf, Sun 'N Rain and Suntop panels. The closure strips are attached to the purlins, which are horizontal supporting members that support a roof. Sometimes purlins are used with rafters, which run perpendicular to the purlins.
See the document section at the bottom of each product's web page for complete installation information.