Religious supply stores sell small crucifixes that are suitable for making rosaries. They also commonly sell beads you can use to represent the Hail Mary and Our Father prayers. Waxed nylon cord is commonly used for making rosaries. Be sure to pick out cord that fits through the centers of the beads you have chosen. The beads should fit the cord easily, but they should not be loose. You’ll need about 3 feet (1 meter). [2] X Research source

Leave a little space for the beads to slide, but not too much. When the rosary is used, the person using it should be able to slide the beads down slightly once each prayer is complete. If you need help tying a knot in a certain place, try this trick: make a loose knot over the spot where you want to tighten it. Place a toothpick on the cord in the spot where the knot should go, then pull it tight and remove the toothpick. [4] X Research source

If your beads are large enough to slip over both tails, you may keep both strings intact. If your beads are too small to slip over both tails, trim the shorter tail with a pair of scissors. Use a dab of clear nail polish or glue to keep the last knot secure as you continue.