Beko 24 Inch Built-In Microwave Installation Instructions - Manual (Page 9)

C. DETERMINE TOP LINE OF REAR WALL TEMPLATE LOCATION UNDER YOUR CABINET
The bottom of the cabinet has three types:
BENEATH FLAT BOTTOM CABINET
Front
Rear
TOP LINE OF REAR WALL TEMPLATE
TOP LINE OF REAR WALL TEMPLATE
At least 24"
STEP-BY-STEP INSTALLATION GUIDE
3
9 / 24 EN Over The Range Microwave Oven / Installation Manual