I'm reading a book called "The Greco-Roman World of the New Testament Era: Exploring the Background of Early Christianity". It's dry but contains a lot of useful information.
Mat 7:13 “Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it.
14 Because narrow is the gate and difficult is the way which leads to life, and there are few who find it."
Every city in Israel had one or more outer gates that were open from sunrise to sunset. It was wide enough that merchants with large carts could enter in but not much more than that. The ones with the larger loads would typically stay around the gate because the way that lead away from the gate would soon become narrower as one moved towards the center of the city. The gate was wide and the way in and on from there was, at least for a little while, broad. Beside or somewhere nearby the wide gate there was a narrower gate that it was possible to enter through at night.
Likewise, a large house would have a wide gate that one could enter through during the day and a narrower gate for when the wide gate was shut. Finding the narrower gate wasn't necessarily a straightforward task, if there was in fact one.
The fact that the gate in verse 14 is narrow doesn't signifiy that few people can enter through, it signifies that he's talking about an alternative route into the city of God, the main route being the way of self righteousness - the one the Pharisees were experts on. It also means that one can't bring all ones luggage with one if one seeks to be able to enter through it.
What about the way onwards ? The Greek word "difficult" means to be pressed, as in implying tribulation. It doesn't mean that the way onwards requires an enormous amount of righteousness in one's walk to qualify, it means that it will be tempting to divert from it because one will be pressed from both sides.
What about the fact that few find it ? It doesn't imply that no more than a few percent of the population can possibly be saved, as in the Calvinist concept of God electing "a tithe". It means that few find it naturally. Placing some heralds around it may be a good idea.