1 Dustin: {crawling through a cramped dark tunnel} There’s one small issue here.
2 Dustin: At the end of the crawlway there’s a secret door, and whoever opens it falls into the next room, taking 1d6 falling damage.
3 Dustin: According to the adventure module as written, there’s no way to avoid the damage.
4 Lucas: Right. So you go first, Dustin.

Dungeons & Dragons adventures were rather different back in the day. There were official published adventures with things like this - traps that had no way to avoid them.

With modern adventure sensibilities, you of course always give the adventurers a sporting chance to avoid such a gratuitous trap. Yeah, haha, not back then!