Now that TS3 has matured, I wonder if this is possible: Build wall/pool right at the edge of the lot. The benefit is of course wonderful because we can build townhouse with different lots now. We have powerful cheats within the lot, I wonder if any cheat or trick that lets us build to right at the edge?

In TS2, I was able to build beyond the lot on second floor onward. Or was it TS1? I didn't allow me to go too far (but able to cross the width of the street), but there was nothing else that "receives" it on the other side, so it was almost for nothing. Now TS3 we can freely designate lot location (not free enough, but better than nothing at all), this may become useful.

Unfortunately I don't think it's possible. Many have tried and got themselves disappointed.

As armiel said, I don't think it is; right now. But, hey, you never know! It does make sense, as is let's us put tiles at the edge, but nothing on those tiles. Well, hopefully somebody will mod or find something.

The best approach is to twist Mootilda's arm until she agrees to make tools for Sims3. Then we can build our walls and shorten the lot by one square all round