DIY Tray Ladder
Darkroom workers with small sinks and the ambition to make large prints often find themselves wanting to obtain a tray ladder. As you can see here, a tray ladder looks a bit like a multilevel dish rack. It is designed to hold three trays, one above the other, often in a vertically staggered arrangement. When using the tray ladder, a print goes (carefully) from one tray to the next, just like the usual arrangement where the trays are laid out horizontally on the same plane. The staggered arrangement of the tray ladder exposes a few inches of each tray, allowing the darkroom worker to carefully move the print from one tray to the one below it as the print processing sequence progresses. I often make 16x20 prints but rarely print any bigger. My darkroom sink permits 16x20 trays, but only if they are turned to a "landscape" orientation and even then the sink is not long enough to contain three trays. So, I decided to build a tray ladder for my darkroom (after unsuccessfully attempting to order one with a backorder period longer than I wanted to wait). I mulled over several possible designs, but in the end decided on a simple design: two sets of aluminum crossbars would support the trays. These crossbars would be supported by four wooden blocks made from 3/4" pine. By the way, this design only works because I use rigid plastic trays. I have seen two basic types of plastic trays used in the darkroom: a rigid, hard plastic type that does not deform easily, and a softer plastic type that can really flop around quite a bit when full of liquid. Again, my tray ladder design depends on the use of rigid plastic trays (stainless steel would work too) because the soft plastic trays would sag too much when supported only in 2 places. The photo below gives an idea of what the finished tray ladder looks like. The wooden triangles are about 11" high. The aluminum crossbars are made from aluminum U-channel stock designed to cover the edges of 3/8" plywood. By the way, if you live in Portland, OR, Parkrose Hardware may do for you as it has for me in terms of weaning me from my tendency to first think of Internet stores like Online Metals as a materials source for projects like this one. Parkrose Hardware has tons of items not easily found in other hardware stores, and it's a real delight to go there with the idea for a project like this and walk out with all the required materials. 
As we all know from the aphorisms about square pegs in round holes, square pegs aren't great matches for round holes. But, square holes are difficult to drill, and in this case we have a square peg (the aluminum crossbars) and I decided to make a round hole in the support block large enough for each crossbar to slide into. I then packed the hole, with the crossbar in place in the hole, with epoxy putty. After this hardened, the crossbars were quite secure in the round holes in the support blocks and the whole assembly stands rigidly all by itself. As you can see, the two support block-crossbar assemplies are not connected to each other. That means I can lengthen or shorten the entire tray rack, allowing me to use either 11x14 trays or 16x20 trays, if the need arises. Here's what the ladder looks like supporting three trays in my darkroom sink (well actually, the ladder only supports the top 2 trays. The bottom tray rests on the sink itself.) 
Because I had the wood for the support blocks on hand, as well as the epoxy putty and the spar urethane used to waterproof the support blocks and only needed to purchase the aluminum crossbar material, the whole project cost about $15. The end result is highly usable!