Box corners for fenestration systems

A fenestration system, comprising:

• a first wall section extending in a first direction and including a first glazing unit attached to a first mullion;
• a second wall section extending in a second direction different from the first direction and including a second glazing unit attached to a second mullion;
• and
• a box corner assembly interposing and operatively coupling the first and second glazing units, the box corner assembly including:
• first and second corner extrusions, each corner extrusion including a base that provides opposing apex and tail ends, the apex end of each corner extrusion being operatively coupled to each other, the tail end of the base of the first corner extrusion being operatively coupled to the first mullion, and the tail end of the base of the second corner extrusion being operatively coupled to the second mullion;
• and
• a strut including a head operatively coupled to the first and second corner extrusions, and a stem extending from the head and being operatively coupled to the first and second mullions.