It's important to provide some sort of transitional border when you join two vinyl floor coverings, especially if they are of different patterns. Many types of transitional strips are available, mostly made of wood or aluminium. Such strips protect the edges of the two vinyl floor coverings from curling and provide a visual border between two colours or patterns, usually at a doorway or pass-through.
Measure the seam where the two vinyl flooring surfaces will come together. Select a metal or wooden transition strip that either blends with the two or provides a complementary colour.
Cut the transition strip to the length needed. If it's a long seam, you may need to use more than one piece. Try to keep the joint where the pieces come together as inconspicuous as possible. Don't put it in the centre, or where traffic may distort or beat down the transition strip and cause a mismatch in the seam between the pieces.
Lay the metal straightedge along the seam as a guide, and use the knife to cut away a 1/8-inch gap between the vinyl floor sheets or tiles. If you are laying fresh vinyl, leave a 1/8-inch gap where they meet.
Lift the edges of the vinyl about 1/2 inch from the seam on both sides, using the knife. Don't lift too high, or you'll curl it and damage the pattern in the vinyl.
Spread floor adhesive between the seams and under the edges of the vinyl. Start at one end, and work your way down a foot or so at a time as you fit the transition strip between the vinyl tiles or sheet vinyl. Use a hair dryer as you work your way down, to warm and soften the edges of the vinyl so it lays flat.
Slide the edges of the vinyl into the grooves under the transition strip, and press it down flat into the adhesive. Lay waxed paper over the transition strip; lay something heavy, such as books, on top of the transition strips as you go. When it's all in place, leave the transition strip weighted down until the glue sets for 24 hours. After 24 hours, remove the weights and waxed paper, and clean up any adhesive spills.
Be sure to do the work at the manufacturer's recommended temperature for the adhesive. If it's too cold or hot when you apply the glue, it can fail to set properly. Clean as much excess glue from the vinyl or transition strip with a damp cloth as you go. Be careful about using harsh chemicals to remove glue. It can damage the vinyl. Test a concealed corner first.
Use a fan or open windows to help ventilate the area when working with vinyl floor adhesive. Wear eye protection when spreading the glue. Keep the hair dryer moving so as not to overheat and blister the vinyl when warming.