The Family Handyman shared this simple no-glue trick. Just buy a length of plastic tubing (which comes by the foot on rolls at your local big box hardware store) and press it in the gap. Measure the space before you head to the store so you know what width tubing to buy. It's as simple as that!
Read More: Countertop Gap Filler from Family Handyman
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(Image: Family Handyman)