How to build a ramp, Step 1
Attach the first module to the house.
We usually bolt to the vertical surface of the first porch step with two concrete anchor bolts, but oftentimes the situation calls for creativity.
It's critical to leave the top edge of the module 3/4" lower than the top of the step. This allows the 3/4" decking that's applied later to run flush with the porch's top surface. We find it's easier to check this dimension by temporarily placing a small scrap of 3/4" material on top of the module.
Frequently, the vertical height of the first step is less than the module's height, and it's necessary to trim a bit off; if done carefully, the module winds up resting on the first step, providing additional support.