Thread one end of a piece of scrap knit fabric through the end of the darning needle (Image 1). Line up the floor mats end to end (the ends that you want to connect), make sure that they are even. Push the needle through one end of the floor mat (Image 2). Bring the needle back up through the other floor mat, connecting the two (Image 3). Tie a knot in the scrap (Image 4).
Repeat the process all the way along the side of the floor mat, connecting the two together (Image 1). Repeat for additional floor mats until you have your desired length. Cut off excess ends of the knit fabric ties, if you want a little dangling free on both sides (Image 2). Enjoy your finished floor mat (Image 3).