Tongue & Groove Patterns (T&G) have the greatest variation in profile - the outline or shape of the board. How distinct or shadowed the line between the boards appears after installation depends on the shape of the edge - the pattern profile you choose.
Traditional TNG patterns are "beveled" on the edges - called a V Edge (as in the pictures below). The depth and angle of the beveling determines how distinct the edges will appear when installed on your wall.
Tongue & Groove SIDING has both a rough and smooth face and is normally graded to the rough face (the best visible face) unless requested otherwise for a higher price. Tongue & Groove PANELING is naturally graded to the smooth face.
Patterns without any V Edge are referred to as Flush-Joint (cedar, pine) or Butt-Joint (redwood). Flush-Joint Tongue and Groove has a similar appearance to classic SHIP LAP Siding.
1x6" Tongue and Groove is the most popular but a wider 1x8" pattern can be selected to have a more rustic appearance. There is also a T&G pattern profile call "carsiding" that has a V-Groove in the center of the board. This gives the illusion of a narrower board (1x4") when installed but with the time savings of a wider board (1x8").
T&G is best milled when fully seasoned - Kiln Dried or Air Dried to the optimal moisture content. Select Tight Knotty grades are popular for their warm, rustic look. Tongue & groove siding is also milled in CLEAR grades, with NO or or very few knots, adding a more formal, streamlined appearance.
Our customer in Kansas installed his 1x6" Tongue & Groove Redwood siding in mid 2015. The factory finish was TWP "redwood" semi-transparent stain. Two years later he is beginning the necessary 2-3 year maintenance coat. On the right you can see how the re-stain brings back the vibrant "punch" of color that had faded under intense sun exposure.