Stainless Steel Duct Cover Dimensions It is essential that we have accurate dimensions for your custom duct cover. Bear with me for a moment, and we'll get it right the first time. In measuring, you will probably find the kitchen wall is not perpendicular with the ceiling, so you will need to measure for the duct cover in 4 places (which I will describe later). But first, some tips to make this measuring easy. I will need exact dimensions from you, and then I will deduct 1/16" of an inch for clearance. If you deduct some, and then I deduct some, we're going to be short. So I need exact measurements. Next, the bending of the tape measure is not accurate enough for what we're doing here. The best way to measure the 4 corners of the duct cover is with a tape measure, and a ruler. If, let's say , the distance between hood and ceiling is approximately 16", hold the tape measure down straight to the top of the hood up 10", and hold ruler to ceiling and measure down to 10" mark on tape measure, which would be approximately 6". By adding the 2 dimensions you will have an exact figure without having to bend the tape measure and estimate. Now, the 4 places to measure: If the front of your duct cover is 12" wide, and 12" deep on the sides, from the exact center of the hood, you will measure over 6" to right front) 5" to right from center line and 12" from wall) and 6" over for left front. Then measure back right corner (against wall 6" from center line) and then measure back left corner. These 4 points are the dimensions we need.