No-Collide Bricks
From Legacy Roblox Wiki
Introduction
Sometimes, while walking about in Roblox you may come across a brick that you can see, but you can walk right through it! It's not magic, it's just something called Can Collide Off. It's a brick that doesn't "hit" other bricks, so things will pass right through it like it's a ghost brick.
Steps
These types of bricks are actually really easy to make on your own. You just have to have the Standard View Setup.
- Select the Brick that you want to be able to walk through.
- Take a look at the Properties window, it'll show a bunch of stuff.
- Look through that text until you see the words "CanCollide". When you find it, un-check box next to it.
- Be careful because the brick won't hit anything, so it will fall through the floor! Check the box that says Anchored to keep that from happening.
That's all there is to it! Now you can make secret passages or doors to use in your map.