Brilliantly illustrated and explained above. You can often forgo the bottom part when it meets a system floor. It's only the top parts that need lining up, the top flat bits. A Plane01 is sometimes a Flat Plane in some properties, as long as you choose the black or dark blue one you are on the right track. Try not to mix props, if you use Flat Planes for the ramps/stairs then try to use the same prop for the floors. You can always make that Flat Plane the collidable and invisible bit (State Tab) and have any other prop with the texture on and non collidable.
Now the red lines. Imagine it's a meat processing plant and a line follows the contours from one red block to the next
through the top of the blocks, 571 (570+1 I think, long while since I did this) clicks high. The height has to be maintained no matter what the angle changes to and it is not guaged by the avatars feet but around its neck as if it is carried on a meat hook through all the different angles. If it drops below 571 or above it you either fall or get locked in place. You will be hooked at 571 above no matter what size of avatar you use. It only appears that you walk on the surface, you are actually hooked and transported (I hate to say like a piece of meat).
You need to deselect all props, as in unlock them all and may have to repeat this sometimes if you cannot get two red lines to show from two different props at the same time. You select first the prop you need to move, which is the top flat section. Next you hover the cursor over the second prop (the ramp) and select "Properties", sliding your cursor to the right of Properties should reveal the second red line. Now the
tops of each need to touch each other in perfect alignment. so that our imaginary meathook goes at 571 clicks up the ramp (red block is 571 high to the top) to the flat section which is also 571 clicks high on the red block that belongs to it. If the
top red block intersection between the ramp and the top flat piece is any higher than 571 or lower then it might need fine tuning to get them corrected. With practice you will do it quite fast.
If you put in another ramp to that top flat piece you could literally throw it in and it would work, in any direction. But the next flat piece would need to be met with the same conditions as above. Keep the thickness of the Flat Planes at the default size or they will lose collidability. Angles should be only 20-30 degreees so use 20 or 340 depending on the rotation used in the property (360 degrees in a circle so 360-20=340), the angle will be 20 or 340, 30 or 330.
Look at the illustration, only the top meets up with the ramp perfectly, the bottom doesn't matter because it never goes past the required angle like the top does, so it just works "as is". See how the top meets the ramp in a triangular shape and the pointy bit at the top of the triangle is where they must meet perfectly.NOTE: My nick and image are from a company. That company allows people to use them both as long as they get permission and a licence. I have that and a certificate to prove it.
"These are not the Druids you are looking for..."
