Common electrodes used for general work include 6010, 6011, 6013, 7018 and 7024, each of which has specific properties: 6010 electrodes penetrate deeply, while 6013 electrodes penetrate less. For much better bead appearance and work on higher strength steels (say for a hitch), use a 7018 rod. For better penetration on thick material, grind the joint to a 30 degree bevel (leave a nickel-width land on the bottom of the groove) and make multiple passes. Alternatively, make the first pass with a 6010 rod, then make a "cap" with a 7018. The 7024 rod is perhaps the easiest to use. Also known as a "drag rod," this electrode's thick flux automatically maintains the correct arc length, which allows you to drag the rod directly along the work piece.