A few tips on installing a stainless steel sink into a counter.
Check all obstructions above and below the counter before drawing the cut line onto the counter top. If you get too close to the back splash, the sink won't go in. Remember, there is an overhang. Check all obstructions below to make sure you leave room for the sink clamps up against a partition wall or the front cabinet framing. Since the sink lip will hide the cut line quite well, use a felt pen to mark the cut line, it is much easier to see against a dark counter top.
If you have to cut closer to the backsplash than your jig saw will allow, you should consider making this cut from the bottom if possible. Otherwise you may have to trim this back cut by hand.
To cut into a square corner, run your saw to the corner, back off two inches, push slightly to one side and run forward again. This will graze one side of the cut and widen it slightly. Repeat this until you have formed a little triangle that will allow you to rotate the blade 90 degrees and run off on the next cut.
While the center of the "hole" is still solidly in place, cut out a hand hold notch in the front part of the scrap. This will allow you to hold onto the piece when you make your final cut through.
Before you push the sink into place, and possibly engage the clamps making it very difficult to remove it, make sure there is either a sealant trim built into the underside of the sink, like on the Blanco sink in the photo, or you put a thick bead of silicone caulking under the lip of the sink to form one. Trying to caulk the joint between the sink and the counter, after it is in place, is hard to do and not very effective. Caulking between the sink and the counter that oozes out a bit, is to be cut off later, and will assure you that no water will get under the sink to damage the counter later. If the sink does not sit down flat to the counter, you should unscrew the clamps and solve the problem. If you leave one corner, or a bit of one side standing high, this area will be a constant cleaning problem and perhaps a source of water damage for the counter top. If you absolutely can't get it flat, or don't want to bother, then squirt the crack full of silicone, let it cure and cut off the excess. Don't leave these gaps open.
We were installing a sink from Blanco Canada.