As the summary states, I would like to see crouching affect an avatar's bounding box. Allowing a taller avatar to crouch, and then move under obstacles, or through passages with low ceilings, such as vent shafts, or caves. Adding the new ability, to "duck", would also be beneficial, given the great variety in height possible within SL, our tallest avatars being over 8 feet tall! Allowing a resident to also remain crouching or ducking until they decide to stand up would be an ideal addition as well. If this is possible, it would open up more options for builders and content creators, which in turn increases the immersive potential of SL. Imagine being in a ruined building, you come across a locked door. Looking around, you see a ventilation shaft. Clicking on the rusted grate it comes free. Kneeling down, your avatar begins to crawl through the tiny passage, which gives you entrance to the locked room. Imagine a small tunnel in the back of a short cave. Crawling through leads to a breathtaking underground chamber. Imagine an 8 foot tall monstrous alien creature ducking to chase you into a room with a low ceiling. To escape, you crawl down the emergency hatch at the end of the room, too small a passage for the gigantic beast! Imagine wandering the wrecked landscape of an island city after a terrible disaster. You come across a street with an overturned truck blocking the path. Seeing there is enough room to crawl beneath you do so and continue on your journey. At present, none of these things are possible in SL, due entire to the fact that crouching seems to have no affect on the avatar's "height". It plays an animation, yes, but for all intents and purposes, one's avatar is as tall standing, as they are crouching. This would be a vital tool for environment designers. I should say it is a vital tool, one that has been conspicuously missing from SL since its inception.