maybe much like the \"do it yourself\" front toe check.
grab a tape measure. run it from the center tread on the driver side tire at the forward and lowest part of the tire to the center tread on the passengers side tire at the forward and lowest part of the tire and record measurement.
do the same on the rearward side of the tire making sure you measure from the same tread and the same height. subtract measurements from eachother and that should give you a rough idea of toe in/out.
hopefully thats not too hard to understand. it's kinda hard to explain.
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say you're looking at the rear tires from the front of the car. the ! is the center tread and the . in the ! is the lower part of the center tread. measure between these two points.
then look at the tires from the rear of the car and take the same measurements.
hope this helps.
good luck.