Drill a number of holes in the mortar joints (a 1/2 inch carbide bit works well in a low RPM drill) and then use a plugging chisel and a drilling hammer (hand sledge) to clean out the mortar, followed by a brick chisel to split off the bricks as needed. Power tools are NOT generally the way to go after the initial dilled holes. Brick walls are not as resistant to hammer blows as you would think.

The issue wot cutting metal is having enough blade teeth in contact with the material being cut to avoid breaking off the teeth. The lower limit is three teeth in contact with the metal being cut, so choose a high enough tooth count blade to achieve this. Slow speed and solid blade contact are also needed. Starting the cut is a little harder in metal. The contact area can be small resulting in the blade slipping on the material and losing teeth until a decent kerf is established. Using a triangular file to start the kerf works well. A few quick strokes with the file and the saw blade can settle in and get to work. A circular saw would not work well for this job. You need to be able to get close to the tree without tearing it up. This job should not need a carbide grit blade. Just buy a 5 or 10 pack of blades and go to town. The blades need to be long enough to cut close to the tree without the saw shoe and body hitting it and damaging the bark. If you start with a file kerf a longer blade length is not nearly as important and can make the job easier.

darthjenn, did you clamp that threshold to your table? That's key to safety. Your hand shouldn't be holding the material, so it can't be available to the blade. (I love my Kreg face-frame clamp, because it will reach into the piece by several inches, and I don't have to worry about whether I have the piece close enough to the edge of the table to get the clamp to hold it) Like you, I live in an apartment, and I'm going to need to come up with some sort of cutting table to use w/ my spiffy new cordless circular saw. One that's heavy enough to not tip, but also easy to store in my highly limited space. (Or, one that can do double duty as a sewing-machine table, maybe.) Also--on the question of which tool is safer: the RIGHT tool is safest. The right blade, the right setup. And control is safest. When you have the right tool, you have control. Sort of like, a dull knife is more dangerous than a sharp one. You push harder w/ a dull blade, and it slips. Personally, I think that once I come up with a cutting table that's got support for the wood and a stable base, a circular saw is probably safer. Mine has two handles, so I'm supposed to use two hands to use it. That means my wood has to be clamped--and my hand won't ever be anywhere near the blade. I also think that taking the battery out between cuts is going to be easier to sustain than unplugging the corded saw. And that's an important safety step. Since I won't ever be doing high-volume cutting, I'm figuring my little cordless will be enough for me. But like you, I'll need to school myself to just wait for the saw to do the work, and to only guide is, and not so much force it forward. That patience you were talking about. Having used a jigsaw, I will say this: in terms of cutting wood, my corded Skil jigsaw was slower than my dad's 7-1/2" corded circular saw, and it was harder to be patient. I'm eager to get started, but I need a cutting table I think is safe.

This one has handles at either end, but might help you explain what to look for What used to be sold in the USA for Boy Scouts is no longer available because of fears that they would garrot each other. Such a thing still exists in Plumbing supply stores, it's for cutting through PVC pipe. It's a saw that's about 1/16" wide and two feet long with metal loops at either end. It works brilliantly on wood, you just loop it around the stem , cross the loops and alternate pulling them.