Final answer:
A dermal puncture on an infant is usually performed on the heel using a heelstick method, which targets the capillaries on the medial and lateral sides of the heel.
Step-by-step explanation:
A dermal puncture, also known as a capillary blood collection, is often performed on an infant at the heel, a procedure known as a heelstick.
The medial and lateral sides of the infant's heel are the preferred sites for puncture, avoiding the back of the heel to prevent injury to the bone. A heelstick is commonly used because it is easier and safer to access the capillaries in this area without causing harm to the infant.