Molotov for clearing ladder. Using default viewmodel, align your right index finger with the dark spot on the wall as shown, or use a full-screen crosshair, or find a lineup that works with your viewmodel. Works with the vent intact, if the vent is already broken the spread is even better. It forces anyone playing ladder to the right where it's harder to avoid getting flashed and cleared by your teammate.

Explained in depth by karrigan here