What is the term for horizontal framing members that run between rafters on opposite sides of the roof frame?

The correct answer is collar tie. Collar ties are horizontal framing members that span between rafters at a location higher than the wall plate, typically located in the upper third of the roof. They serve to prevent the rafters from spreading apart due to the weight of the roof and the load of snow or other environmental factors. By doing this, collar ties help maintain the structural integrity of the roof and keep it aligned properly.

In contrast, a ridge board is the horizontal member at the peak of the roof where the top ends of the rafters meet. It does not provide support in the same way as collar ties, acting primarily as a nailing surface rather than a structural reinforcement against rafter spread. Purlins are horizontal members that provide support for the roof sheathing or decking and are usually installed perpendicular to the rafters, but they are not located between rafters in the same manner as collar ties. Rafters are the sloped framing members that directly support the roof and extend from the eaves to the ridge, but they are not horizontal framing members that connect across the structure.