Rafter as a noun is one of a series of sloped beams that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads. while Purlin as a noun is a horizontal structural member bridging two or more rafters of a roof.
Part of speech: noun
Definition: one of a series of sloped beams that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads. flock of turkeys
Part of speech: noun
Definition: A horizontal structural member bridging two or more rafters of a roof.
We hope you now know whether to use Rafter or Purlin in your sentence.