A portable saw has its clear benefits as a tool, but if you wish to make precision cuts then a table saw is the better option. Rather than going out and buying an expensive second tool, it's possible to convert your portable saw into a table saw for these tasks.
Ensure that the power tool accessory table has a rectangular slot cut into it to accommodate the circular saw and blade. This slot should be 8 inches long and 3/4 inches wide. If a slot is not already present, you will have to create this slot using a saw.
Secure the portable saw to table's underside with brackets. Make sure the blade passes through the slot and the blade and guard extends to the upper side.
Measure the width of the table as you want it to be when completed. If, for example, you want an 8-inch board, face the saw and measure 8 inches from the left of the blade. Mark two points here -- one at the front and one at the back of the blade. These marks will be used to help you set your guide board.
Connect the saw to a power supply and position the foot-controlled switch to a place that allows you to switch the saw on or off while cutting the board.
Position the 1-by-2 guide board in line with the two marks and clamp it securely into place.
Always wear safety goggles when using an electrical saw.