Boreham Wood's Delano Sam-Yorke played a one-two with with Harry White before firing home the only goal.
Adam Boyes' header hit the bar for Guiseley and Sam-Yorke struck the inside of the post for the Wood.
After 20th-placed Halifax's surprise win over Forest Green, the Wood now sit 19th on 47 points, while Guiseley are 21st on 46 points with one game left.
Boreham Wood defeated fellow strugglers Guiseley to leave the Yorkshire club in the National League relegation zone.