Be sure to cook this on a DRY day! Pour sugar into heavy-bottom pot (such as pressure cooker). Stir in Karo, water and evaporated milk. Let come to boil over medium heat; stir in salt. After boiling a while, stir in pecan halves and lower heat a little. Stir constantly, till candy reaches soft-ball stage. DON'T OVERCOOK! Remove from heat. Let 1/2 stick of margarine melt in. While candy is resting, set out waxed paper. When candy has cooled enough to not melt wax, stir in margarine and drop by tablespoons. Yields 15 18 pralines.