SI 1   Located on the 5th digit of the front foot, on the mid-lateral aspect of the nail, in the sensitive ridge of tissue. Insert a 13mm needle to about 3mm depth.
My Graphic
The above picture is of the lateral aspect of the right foot of the dog showing the location of the first point on the Small Intestine meridian, SI1.
Note that it is situated on the mid-lateral aspect of the nail of the 5th digit.
In practice, you need to be able to see the lateral aspect of the nail-bed of this toe. This might require clipping of hair. Note the ridge of sensitive tissue that surrounds the base of the nail like a collar. The needle is inserted into the highest part of the ridge (ie not into the junction of the nail and the nail bed) and parallel to the toe. Because it is painful it helps to compress the whole foot tightly in your hand but leave the point exposed. This technique allows for almost incident free insertions in the dog and cat. Replace the foot on the ground after inserting the needle. The needle should now lie parallel to the ground.
My Graphic
The above picture is of the lateral aspect of the front right foot of the dog showing the location of SI1. Notice the placement of SI1 at the mid-lateral aspect at the base of the nail of the 5th toe.