This rug appears to have been created by knitting with string a rectangle about 17" x 25 inches. Medium to heavy weight string is used to knit the garter stitch foundation. Then colored scraps of cloth about 3" long and between 1/2" and 3/4" wide are threaded through every other stitch of the knitted rectangle. The final 3-4 rows are scraps of dark blue or balck. The guage of the knitting appears to be about 5 stitches per inch.

finished scrap rug measures approximately 20" x 28"
larger view

close up of the scraps

back of the rug - cloth covering and the edge scraps

inside the cloth covering of the back shows the back where the edge scraps have gone through the knitting

inside the cloth covering of the back shows the back where the colored and edge scraps have gone through the knitting

edge of knitting seen from the back side where the cloth is not quite covering the knitting

front side - green scrap strip goes through the knitting

front side - green scrap strip goes through the knitting

right side of rug - showing garter stitch knitting

tape measure showing that the garter stitch knitting is about 5 stitches per inch