How to Cut Inside Corners for Wood Trim


Wood molding and trim add an elegant touch to any room's decor. There is little limit to the amount of detail and eye appeal possible. Measuring and cutting wood trim angles to fit perfectly determines the final look. The most cost-effective tools for cutting wood trim angles for inside corners are the miter box and miter saw. These tools are commonly sold together as a set and are available at most home improvement stores.

Things You'll Need

  • Tape measure
  • Measure the flat length of the wall where trim is to be installed. Take the measurement from the inside corner of one end of the wall to the opposite inside corner of the same wall. The result is the length the trim is to be cut to fit the wall.

  • Set one end of a wood trim piece into the miter box with the decorative side facing up. The side of the wood trim that will be against the wall when trim is installed should be sitting flat in the miter box. If the wood trim has a top and a bottom, note the side of the miter box on which the bottom of the trim is located.

  • Adjust the wood trim in the miter box until the end lies slightly across the angle line marked at 45 degrees. Place the miter saw into the miter box into the 45-degree angle cut line. The cutting edge of the blade should be angled toward the end piece of the wood trim.

  • Hold the trim piece firmly in place within the miter box and saw the angle off the end of the wood trim. The cut angle in the wood trim will keep the saw at the appropriate angle to maintain a 45-degree cut. Once this end piece is cut off, remove the trim from the box.

  • Measure the trim piece along the back, undecorated surface from the longest angle to the opposite end of the trim. Mark the wood trim precisely at the point determined from measuring the inside corners of the wall. This mark will indicate the longest end of the angle soon to be cut. Extend the line just marked across the entire width of the wood trim where it can be easily viewed from the side.

  • Set the wood trim into the miter box with the newly marked end of the trim perpendicular to the opposite 45-degree angle slot in the miter box. The newly marked line should be aligned exactly with the lowest point on this 45-degree angle slot.

  • Set the miter saw into this angle slot and prepare to cut the second angle on the wood trim. The trim should be setting in the box with the decorative side facing up, and the unfinished side facing down. Additionally, the saw should be cutting away from the measured piece of wood trim that is to be fitted to the wall.

  • Hold the trim firmly in place within the miter saw and cut the angle just marked at 45 degrees. Remove the trim from the miter box and test-fit it in the section of the wall it is to be installed. If slight adjustments are needed, trim the edges with the miter saw and miter box.

Tips & Warnings

  • Measure the length to be cut a second and third time before cutting the trim to ensure the proper length on the trim has been marked for cutting.
  • Miter saws are very sharp. Wear gloves and goggles when cutting with a miter saw and miter box combination.

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