What is the name of the building member that primarily connects the rafters at the top?

The correct answer, collar tie, is a key structural component in roof framing. Collar ties are horizontal members that are installed in the upper portion of a roof's structure, connecting opposing rafters to help resist outward spreading forces. Their primary function is to stabilize the roof by preventing the rafters from separating under the weight of snow or other loads, thereby maintaining the integrity of the roof and the overall structure.

In contrast, frame ties serve a different purpose by providing lateral support to the walls and preventing collapse. Floor ties are typically used in floor framing, connecting floor joists, and are not involved in the roof structure. Ceiling joists run horizontally across the top of walls to support the ceiling and are different from collar ties, which operate higher up in the roof system and focus on keeping rafters in alignment. This distinction highlights why the collar tie is the appropriate choice for the member connecting rafters at the top.