Cut Big-Time Joints with a Small-Time Saw
If your circular saw leaves the shelf only to trim deck boards or knock down sheets of plywood to rough size, you're underutilizing it. You can also use it as a joinery tool for parts too unwieldy to dado on a tablesaw.
Start with the saw
Start by preparing a saw for joinery work. For cleaner cuts, set aside that 24-tooth rough-duty blade in favor of a 40-tooth regular-kerf blade. Then set the blade 90° to the base plate.
Next build the cutting guide shown below. Measure from the left edge of the saw base to the blade (when viewed from the top), add 1/4", and glue the fence that distance from the right edge of the guide. Glue a cleat 90° to the fence on the underside of the guide.
To prepare the guide, place it on a piece of scrap clamped to your workbench with the right edge overhanging the bench. With the left edge of the circular saw base pressed firmly against the fence, cut off the surplus 1/4". Now you're ready to start cutting joints.