I like to incorporate some goofy pieces of wood into my work. Many of them have structural issues or voids that need to be addressed before they can be used in a project. Epoxy works great for filling and stabilizing knots, cracks, voids, and other defects in wood.
Products Used [Affiliate Links]:
West System Epoxy Resin (Gallon): http://amzn.to/25TYH7y
West System Epoxy Slow Hardener (Quart): http://amzn.to/25TYKAr
Metering Pumps: http://amzn.to/1qicuEr
High Density Filler: http://amzn.to/20tVFmA
Transtint Medium Brown: http://amzn.to/23nL4Ps
Transtint Bright Red: http://amzn.to/1qicy6V