Rooflights Snapping to a triangle shape when I want them to be rectangular

Good afternoon, 

I am struggling to add rectangular rooflights into my model since in plan view the tool is snapping to a triangle shape. See image: https://gyazo.com/005cc1bb886c71ed508c5f8753af3954

And see 3D image of the triangle roof rooflight:

https://gyazo.com/e83678388d4a0f375635b9d26ca097db

Any information would be valued

Kind regards

Toby Norris