It's nice to have place where you can quickly wash your hands when you've been mucking about with soil or just weeding without your gloves on, or to wash the soil from your radishes, onions or beets before bringing them into the kitchen.
I have a simple one for my kitchen garden and a more elaborate one for the main garden, which is in the back 50 feet of my 160 foot deep lot.
Step 1: Water Storage and Dispenser
These soap jugs last a long time in a household, but eventually they go out in the recycling. In the store they come with a measuring cap cover. I like to recycle ones that still have the cover. It provides some protection to the push button from the elements during the summer, but that rubber does eventually break down and split. If you find two of the same brand (different brands have differently sized spigots), take the spigot off the second one to have as a spare since the plastic container will often last longer than the spigot's rubber.
Usually these containers are not rinsed out when being tossed, so do that. I use just a cup of water is the first rinse so that I can recycle the dilute detergent for hand laundry. Just gently swirl the water so you don't build up a lot of suds. Adding vinegar to the last rinse cuts down on some suds as well as helps get rid of the detergent odor.
If I get one to set up early in the gardening season, I know that the first few fills will be used simply for hand and small implement washing and I don't get fussy about getting every bit of suds out.
The spigot may suffer a build-up of dried up detergent. So soak and use an old toothbrush to scrub it out. Work the spigot push button under water to get the material out of the spigot's insides.
Step 2: Catch Basin
You could just let the water go to ground, but sometimes I like to have sitting water to rinse small things in. Also, if you are simply washing dirt off your hands, implements, or vegetables, you can reuse the water for plants.
Your basinl can as simple as small bucket or as fancy as the glass front of an old front-loading washing machine. I prefer the glass myself.
Step 3: Setup and Use
You can fill the container either through the small cap (there to loosen so air can enter and ease flow of contents through the spigot), or through the spigot hole (the spigot is actually a large cap).
The container can be set on anything strong enough to hold its filled weight with the spigot over an edge. Set the catch basin under the spigot. Your setup can be as simple as a stump with the basin on the ground or a picnic table with the basin on the seat. When my Australian BBQ gave up the ghost, I removed the burner/grill setup and built a shelf across those now-empty supports. It became my kitchen garden workbench and I set up the wash station on one end of it. In the main garden, I have a potting bench adjacent to a laundry tub on which I set the container; I also have a bucket under the drain hole of the tub.
To use, loosen the small cap to let in air. Take off the protective cap. Push the red button on the spigot to get water.