In spite of my good intentions my poor carpentry skills got the better of me!
The HO scale Pseudo-Soo Line traverses the swamps and bogs of northern Wisconsin so you know that the topography must be fairly flat. None of this up and down the Rockies routine suited the patriarch of the Pseudo-Soo. Therefore, when I built the “new” Pseudo-Soo Line in St. Peters in the very early aughts (that is, in 2000) the intent was to make the darned thing as level as possible both to mimic the timid terrain of the tundra but also to make switching cars a piece of pie.
I used a “water level” (also called a “water level device,” “water manometer,” or “water tube level”) to mark the primary bench work height every eight feet or so around the layout room. It was a first for me and I was far from expert. The technique goes back many years. Heck, old man Archimedes himself might have invented it! In the days of steam the water level was used to assure that the frames for the locomotives were perfectly level before all the pieces were permanently and solidly pinned together. If Lima could do it in 1925 for the two 40,000 pound main side frames of a 2-8-4 Berkshire I should be able to level the bench work in my basement.
A simple water level starts with an everyday garden hose. Add sight glasses at both ends, and fill with water. Of course, you have to open the opposite end to the atmosphere to let all the air out. Home Depot had the sight glasses in stock (probably primarily for leveling mobile homes) so it was not a particularly esoteric plan. Once you have it set up you can achieve excellent accuracy over relatively long distances, even around obstructions and corners. Thus, I should have been able to establish a base line height on the house support post in the center of the layout room and accurately transferred the level to anywhere else in the basement. If done right one can achieve accuracy of hundredths of an inch. In retrospect I now realize that my 50-foot hose was probably too long for the situation and I probably did not have all of the air bubbles out of it. In any event, I ended up with some minor ups and downs in the layout, just as there are in the swamps of Wisconsin! Prototypic topographic perfection! Unfortunately, with the super free-rolling trucks of today any car left standing on even those minor grades will seek its level somewhere else, so much for sophisticated planning and execution.
Nylon mono-filament fishing line to the rescue! I bought a 275 yard roll of 20 pound-test line on sale for a buck. I chucked a #68 drill in a pin vise and hand drilled holes about a half inch deep between the ties wherever I felt a need for a little restraint. Depending on your roadbed construction you might try drilling the hole through a tie although it will make a stiffer brake. If you are using cork or foam roadbed over Styrofoam you can just push a quilting pin or perhaps a T-pin into the material to form the pilot hole for the fishing line. In any case cut off about two inches of line. Right off the roll the fishing line will have a bit of a curl so it might be useful to install the line with the curl pointing upgrade. That should slightly increase the resistance to the downhill load and decrease the effort to push the car up the hill pass the brake. Dab a little gooey cement on one end of the piece and shove it in the hole. Rubber cement, Walthers Goo, clear silicone caulk, “tacky” glue, Woodland Scenics accent glue, and many others will all work to lock it in place. After the cement dries use a two axle truck from a freight car to establish the correct height for the brake. Photo 1 shows a brake installed before cutting it to length. The brake works best if the fishing line extends to about the top of the axle or a little less. Use a rail nipper or fingernail clipper to accurately cut the fish line to length. Photo 2 shows the nipper ready to snip! You will get a little clickety-clack when cars pass over the brake but that should be music to your ears.
A single brake will hold several cars on grades of 1% or so. If most of the cars to be parked on a given track are of similar length you can place multiple brakes one or two car lengths apart to hold more cars. Photo 3 shows three hoppers held by two mono-filament fishing line brakes on the 3% grade up to my coal dock. The brakes are about 8.5 inches apart as shown by the yellow-headed quilting pins that I temporarily installed for illustration.
If you work in N scale you might want to try a lighter weight fishing line; if in S or O scale a heavier line or perhaps fine music wire would be the way to go.
If I had to do it over again I would use one of the wonderful and relatively inexpensive laser levels that are now available to establish my base line in an open layout room as I had when I started. Of course, the room was cluttered with walls of moving boxes. I would have probably had to move a lot of boxes to get the job done. If your layout wanders through several rooms a water tube device might still be a good choice to establish your own Water Level Route to avoid the need for brakes. On the other hand, if your layout is designed for Rocky Mountain highs you might still need a brake here and there to keep the gons and the goats from rolling down the mountain.