Sy'kl and Morthil grab a large rock (weighing roughly 30lbs) from outside, carry it back to the "trap" spot, and heave it on from about 15 feet away... nothing happens for a moment, then the entire ceiling suddenly pistons downward at astounding speeds, smashing the rock into fragments and stopping roughly 4 inches from the ground, then slowly retracts back upward, the seams on the ceiling slightly more visible...
Jirandiel and Sceorio look on, a bit startled at the force...