Step 1: Measure the width of your window frame to determine the shelf width. (Shelves generally look best if they are the same width as the window or a couple of inches longer on each end.)

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Step 2: Use the length of your shelf to determine how many brackets/corbels you need, spacing them every 2-3 feet. Container plantings can be heavy so plan for spacing that allows you to anchor the brackets to wall studs for adequate support. 

Mark the spacing for the brackets/corbels. Make sure your horizontal marks are level so the shelf won’t sag.

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Step 3: Attach an L-bracket—we used 3/4x2x2 inch brackets—to the top of each shelf with a stainless-steel screw. The vertical arm of the shelf bracket should extend above the corbel.