Sprinkle yeast over warm water in a large mixing bowl; stir until dissolved.
Add shortening, salt, and half the flour. Beat, with a wooden spoon, until smooth-about 2 minutes (or mix in a heavy duty mixer with a dough hook)
Gradually add remaining flour, mixing with hand until dough is stiff enough to leave side of bowl.
Turn dough out onto lightly floured board. Cover with bowl; let rest 10 minutes. Knead 8 to 10 minutes, or until smooth and elastic.
Place in lightly greased medium bowl; turn dough, to bring up greased side. Cover with towel; let rise in a warm place (85F), free from drafts, until double in bulk-about 1 hour. When two fingers poked into dough leave indentations, rising is sufficient.
Punch down dough with fist; turn out onto lightly floured pastry cloth (if you don't have a pastry cloth, a floured countertop will do).
Preheat oven to 450 degrees F. Spread oil over bottoms of 2 (12-inch) pizza pans.
Knead dough 3 to 5 minutes. Divide in half; roll each into a 12-inch circle.
Fit each circle into prepared pan, pressing edges onto side of pan. Spread with desired filling.
Place pans of cookie sheets. Bake pizza 25 minutes, or until crust is golden brown and filling is bubbly.