Measure every used 2 by 4 before you start any project; 2 by 4s are dimensional lumber. Lumber is sold according to approximate, not actual, dimensions.
Thus, 2 by 4s begin as two-inch thick by four-inch wide boards, but millling and processing reduce them by as much as half an inch in both dimensions. According to the Advantage Trim and Lumber Company, "This measurement refers to the thickness and width of the lumber and the length varies.
In reality, these measurements are not a true measurement of the lumber thickness or width. The true measurement of a 2x4 is actually about 15x35.
When the board is first rough sawn from the log, it is a true 2x4, but the drying process and planning of the board reduce it to the finished 15x35 size Square and plane boards before use. Used 2 by 4s may be warped, have dry rot or mold damage, or have splits, holes and other damage.
Use a carpenter's tri-square to verify that each board has only 90-degree angles at each end. If the board end is not 90 degrees, draw a line across the board with a carpenter's pencil where you need to cut the board to make it so.
Use a miter fence and table saw to cut across the line. Set dry-rotted or moldy boards aside.
Compost and Mulch
Boards with dry-rot can be composted as long as they have not been treated with any toxic chemicals. Unfinished lumber is usually safe, but any lumber with visible stain, paint or other coatings should not be used for compost without testing.
Rinse moldy boards with bleach and lay them on racks in the sun to dry, or dry them in a kiln after the bleach has time to evaporate. If the bleach does not remove all traces of mold, try planing the boards.
If this works, you will be able to use the boards to build something instead of sending them to the compost heap Use a wood chipper to grind each board into mulch or sawdust. Add only a few board's worth of mulch to your compost pile at a time.
Wood mulch is considered a brown ingredient. According to vegWebcom, "Wood products belong in the 'browns' category, because they are fairly low in nitrogen.
Some sawdusts, especially from broadleaved/deciduous tress, will break down quickly in an active compost pile. Others, especially from coniferous trees, will take longer to decay.
Stir sawdust thoroughly into the pile or use very thin layers. Coarse wood chips will very slowly decay, and are probably better used as mulch unless you have lots of time to wait.
Be sure not to compost chips or sawdust from any sort of chemically-treated wood -- you could be adding toxics like arsenic to your pile if you do".
Use old 2 by 4s to make a balance beam. You will have to cut two 24-inch pieces from one 2 by 4 to make the feet for your balance beam, and an eight-foot long 2 by 4 for the beam itself.
Draw a line 10 inches from each end of each 24-inch 2 by 4. There will be four inches left between the two lines.
The lines will provide a guide to center the eight-foot long beam on the two feet. The feet will support your balance beam.
You will need a power drill and 3/4-inch diameter drill bit to make lag bolt holes all the way through the feet and halfway through the long beam. Use lag bolts, which look like oversize screws with bolt heads, to hold the feet and the long beam together, so that the surface of your balance beam will remain smooth.
If you used regular bolts instead, you would have a hole all the way through the beam, and risk injury due to catching feet or other body parts on the ends of the bolt or the nut holding it in place.
If you cut 2 by 4s into equal length pieces and butt them together, you can create butcher blocks of varying length, width and thickness. Lay squared and planed 2 by 4s on their two-inch sides for a four-inch thick block, or on the four-inch sides for a two-inch thick block.
Use carpenter's glue and a table vise to clamp them against one another while the adhesive cures. Use a belt sander and coarse through extra-fine sandpaper to create a uniform, smooth surface on all sides of your butcher block.
You can use beeswax or food-grade mineral oil to protect your butcher block. According to WoodZonecom, "Butcher blocks should be finished regularly with a mineral oil and a beeswax coating to maintain their beauty and keep the wood from warping and cracking.
Modern polyurethane and varnish finishes that are used on most furniture today should not be used on butcher blocks. These finishes are hard and sit on the surface.
Cutting on the butcher block will break through this barrier and allow moisture into the wood".