Spats evolved from spatterdashes, or cloth enclosures that would protect soldiers' boots from "spatters" of mud and dirt. By the early 20th century, they had made their into the world of high fashion, and they were popular with the upper classes. In the 1920s, gangsters, who want to show off their wealth, had picked up the style. White spats were popular at the time since they showed that you were privileged enough to be able to keep out of the mud and dirt. Today, spats can be used in historical or fantasy costuming, or to make summer shoes look like autumn or winter boots.
Find or make a pattern. You can download patterns online, or make your own by wrapping fabric around your ankle, marking it with pins, and cutting it to size.
Place the pattern on a piece of fabric folded in two, with the right sides together. The doubled-up fabric will allow you to make inverse left and right spats at the same time. Fabrics that work well include tweed, corduroy or canvas. For a genuine 1920s look, use a white material.
Draw a line around the pattern for the spats in fabric pen.
Draw another line 1/2 inch outside of the first line for seam and hem allowance.
Cut at the outer line.
Attach any pieces that need to be sewn together.
Hem the edges of the spats.
Wrap the spats around your ankles while wearing the shoes to make sure they will fit. Make small marks on the wrong side of the fabric for where buttons and button holes will go, and check these marks by pinning where the buttons will go.
Sew and cut button holes, and add sew on round-topped buttons that match the fabric.
Put on the spats. Measure a piece of elastic from the inside to the outside of each spat, around the bottom of your shoe. The elastic should fit just in front of the heel portion of the sole.
Sew the ends of the elastic to the inside and outside of each spat. Sew them so that the ends are tucked inside the spats.