I am installing slate in my hallway. I have 5 doors ( = 10 door jambs) to shorten so I can slip the tile underneith the door jamb. I checked ebay for electric door jamb saws and found $150 on up. A little too much to justify for my project so I went to Home depot and purchased one of those offset handle flush cut hand saws for $15. After the first door jamb I decided "SCREW THIS!". I took the saw to the garage and removed the pin holding the handle on then removed the wooden handle. I pulled out my dullest sawsall blade and snaped to about 2" long in my vise with a hammer. I then welded the broken saws all blade to the flush cut saw where the wooden handle used to be.
SWEET!!!!!!!!!!
I took my new flush cut / sawzall blade and chucked it up in my sawzall. I set the sawzall to a low speed (about 1.5 - 2) and it took about 30 seconds per jamb.
I have decided to take out an "internet patent" on my new blade so if you read about this on the internet and use it please send me $.50... Ha... :-)
P.S. You could probabally drill the sawzall blade and bolt it to the flush cut saw if you aren't blessed with a welder.