To begin making tongue and groove boards you first must decide to use either a table saw or a router.
Make my own tongue and groove siding.
Carefully slice the back part of the groove of your replacement board but leave the front part of the groove attached.
Tongue and groove joints can easily be made with a router when using the right bits on a proper router table.
Depending on how the pieces fit together some jointed sidings can be fully attached by blind nailing through a tongue or underlap that will be covered by the course above.
Insert your new board s tongue into your old board s groove and lay the new board s front groove over the other old board s tongue.
You can use your circular saw set to the depth of just the back part of the groove.
Check to make sure the siding you choose has a successful track record in your region.
Other types require face nailing as well.
Calculate sqft to lft coverage needed vertical siding applications require horizontal nailers blocking or other wood framing members spaced no more than 24 inches on center.