To succeed in the kind of woodworking that is built in a shop, You Need FLAT lumber. You also need it to be, for example, actually 3/4" thick. Ordinary 3/4 lumber yard lumber is sold as 1 x 2, 1 x 4, etc which are actually 3/4 x 1 1/2. and 3/4 x 3 1/2 respectively and THEY ARE NOT FLAT and the thickness is badly controlled. Great if you plan to nail them down, but they will not give good results for furniture. The following describes what the lumber industry provides for shops to work with:
Wood that is suitable for fine woodworking has been processed to a less finished shape and size than ordinary finished lumber that is mostly intended for construction use. Here are the steps from a Raw log at the lumber mill to shop ready lumber:
The log is sliced with a giant band saw to a thickness expressed in quarters (of an inch). Four quarter lumber is 1" plus a bit extra for variations from the saw. Eight quarter is 2" plus a bit extra. These are the most frequent thicknesses, and some species are available in 5/4, 6/4, and much larger. At this stage it is 4/4, 8/4, etc green lumber.
Next, the boards are air or kiln dried. Air drying takes at least one year per inch of thickness. It is rare, but if you are offered air dried lumber, it often is only very slightly dried: Be Careful!
Once the lumber is dried it has almost always warped some. A side view of the edge of a long board of rough-sawn lumber may look like this (exaggerated) image:
To make a 3/4 flat board out of, for example, a 4/4 rough sawn board the flat board would have to fit entirely within the curved surrounding of the rough sawn piece. Since it is long, the total rise of the bend is almost always too much to fit a 3/4 flat board inside.
So, they don't even try. Instead they use a planer to smooth the faces and bring it to an equal thickness everywhere. A thickness planer does just that: equal thickness, smooth face, still bent. What you see here is a 4/4 board that has been planed to just 1/16" less than the full 4/4 rough thickness. It is called "Four quarter hit and miss lumber" Eight quarter hit and miss is 1 15/16 thick, and so on. It may have patches that are still the rough sawn surface, hence the hit and miss planing description.
Ninety % of the lumber used in furniture and other fine woodworking is purchased as hit and miss. It has the advantages that you can see what it looks like, and if you buy it 1/4" up from your final thickness (4/4 to make 3/4 flat pieces) you still have 3/16" of surface you can remove in flattening your lumber. All that is needed to fit a 3/4 flat board inside the hit and miss board shown above is to cut it shorter first. Obviously, the makers of lumber cannot predict the lengths you need, so you buy it fat, cut it shorter and THEN flatten it.
NO, I am NOT going to leave you with no idea where to get hit and miss lumber
We are very fortunate to have a company here in Seattle, that not only has racks and racks of a very large variety of beautiful species almost all hit and miss, they also let you pick your own. Shop lumber comes in random widths and lengths so if you order it sight unseen you must buy about twice extra to assure that you can match colors and get the cuts you need. When you can pick it yourself, you can make a much more beautiful piece of work with much less material. Check them out: CROSSCUT HARDWOODS