Here's a brief breakdown of the rules of "Pitching Washers". These are the basic "Pit" rules and most traditional version of the game of washers.

Game Area
Two 3" diameter PVC cups (3.5" long) are placed in the ground deep enough for the top of the cup to be flush with the ground. It's a good idea to have a clear, flat area of soil around the cup (36" square will work). The cups are placed 21' apart - measuring from the center of the cups.

Starting the Game
Each player will pitch (underhand) one washer toward the opposite pit, this is also known as the "diddle". If you’re playing teams one player from each team will pitch. The player with the closest washer will start the game. After the game has started the team that scored last will pitch first.

Scoring
Only one player may score per round but the scoring player will score points for ALL washers closer to the cup than their opponent.
Washers are pitched underhand from a line event to the front of the cup toward the opposite cup. The starting player will pitch their four washers followed by their opponent, the idea being to land in the cup if possible and if not - as close as possible.
A washer landing inside the cup, a ringer, scores 5 points.
A washer hanging over the lip of the cup is called a leaner and is worth 3 points.  
A washer closest to the cup but outside the cup scores 1 point.

If two players pitch a ringer or a leaner, those will cancel each other out and you will score the next closest washer.

Object
The player or team reaching 21 points first wins the game.
"Skunks" can be called along the way if an advantage of 11-0 is taken.