Really not something I'd do, but is it really of any use? From the description,
An arch makes your house more unique than just dumping a driveway or garage next to it. Here is how to create a driveway arch in Sims 2.Riiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiight! I think sanity is at an all-time low, with how-to guides topping the list. I know WikiHow's got interesting things now and then, but this... it takes the cake!