I have a spline sketch that I want to work off of. If I use this spline as the example:

How do I create a perimeter around/within it such that the perimeter maintains the spline's shape? I'm looking to make a perimeter that has a known distance from the original spline.

What I'm not looking for is simply re-scaling the spline. Doing so doesn't give me a fixed distance between the original spline and the new perimeter sketch.

If the question was unclear I can try to explain it in another way. Thanks!