Combine chocolate chips and shortening in double boiler over hot (not boiling) water. Stir until chips melt and mixture is smooth. Remove pan from heat but keep chocolate over hot water. Dip pretzels into mixture and coat evenly. Shake off excess coating. Place pretzels on cookie sheet lined with wax paper. Chill until coating sets, about 15 minutes. Gently loosen from paper and store in refrigerator until ready to use. Makes 50.