How do I evenly space my knots for my hanging craft project? I'm attempting to make a ladder-like structure completely out of fishing line. I'm trying to avoid any extra materials such as rings, hooks or crimping sleeves because I want this to be as low-visibility as possible.

The project will consist long vertical sections connected by horizontal segments at regular intervals.

Here's a diagram of a portion of what I have in mind:


The black circles here would be knots, and I need to be able to space them the same vertical distance apart each time.

The red sections connect the two verticals, and I need to be able to tie them to the the bottoms of each vertical section. Again, each segment should be the same length.

My problem comes in being able to keep the distance between knots equal. I tried a double slip knot, but I can't seem to control the length well enough since I need a knot at both ends of the segment.

Is there a way to get them evenly spaced, within about 1/8th inch tolerance? It doesn't need to be the same knot at either end of the segment, if that helps. I'm not sure if there's a specific knot combination I need to use, or some technique/trick (like using straws on thicker material) that will help me space whichever knots I go with.

The ends don't have to be tight knots, but could be open loops, as long as I can make the length from end of loop to end of loop consistent.

This project will end up supporting weights which will hang from the horizontal sections, so it's important that the knots withstand the weight. There'll be about 1 pound per horizontal segment. This means that if I make 5 sections, the top will support all the weight (5 lbs) and the bottom will only support the last pound.
First thing that comes to my mind, why don't you try it in the same way as bobbin lace? In your case, that means a large cushion (maybe a(n old) mattress), as stiff as possible, and use pins to get/keep the knots in the right places.