Mom's Peanut Butter Cookies

1 1/2 C flour
1 t baking soda
1/4 t salt
1/2 C shortening
1/2 C peanut butter 
1/2 C brown sugar
1/2 C granulated sugar
1 egg
1/2 t vanilla 

Chill then roll into balls
Press with fork
Bake at 375 for 12-15 minutes