In a large bowl, dissolve yeast in warm (110°) water in a large bowl. Stir in sugar and salt until dissolved. Add flour, mix well. Turn onto a floured surface, knead 5 minutes. Divide dough into 16 equal pieces. Roll into thin strips; shape into pretzels. Place on a well-greased baking sheet. Beat egg yolk with water, brush on pretzels. Sprinkle with salt; bake at 425° for 15 to 20 minutes, or until golden. Makes 16 pretzels.