This style of overlap is uncommon for prefab fireplaces but some units are best suited for 3-sided overlap doors. This type of fitment requires a hearth or floor for the door to sit on, which also should be level with the firebox.
Although this fitment is rare for prefab fireplaces some do require them which is why we offer a variety of different doors. All of these doors come with mounting brackets and we offer a few different types depending on what your fireplace opening requires.
If you aren't sure what type of fitment you need you can always give us a call or fill out or contact form and one of our talented staff will guide you through the process!