A grooving sled for use with a pre-formed groove blade and hot knife, for making grooves in expanded polystyrene foam boards or walls. The grooving sled includes a built-in straight edge guide, one of two cutting position margins, and a stabilizer plate that fits inside a freshly-cut groove to keep the grooving sled straight while operating along the cutting layout line established on the board or wall. The stabilizer plate aligns with the groove blade by use of an angular adjuster, and if necessary, an insert bar. The stabilizer plate can also be adjusted vertically.