The other day when I was framing the wall for a client’s back hall (see this post), I used this quick trick to make a notch in the 2×6.
First, if possible, hold your piece in place so you can mark how wide the notch needs to be. Otherwise, you can measure as well.
Don’t get out the jig saw to cut the notch out. That takes too long! Go to the chop saw and cut the edge of the board to the right depth. Usually, it doesn’t have to be terribly accurate, as long as it fits.
After you’ve made these cuts, pull out your hammer and whack it! With a couple good hits, the notch should just break off along the grain and you’re done. Once you’ve done it a couple times, you can do it very quickly- way faster than making a notch with a jig saw.
This only works if you are cutting across the grain so that the notch will split off. Also, don’t try this with something that has to look pretty. It works with framing because it will be covered. It wouldn’t work so well with door casing, for example… 
-Peter
