Final answer:
Incorrect placement of the rubber band on perm rods can cause uneven curls. It creates a tight spot, leading to indentations in the curl pattern. Proper placement ensures consistent tension and avoids this issue.
Step-by-step explanation:
Incorrect placement of the rubber band of perm rods can lead to band marks or uneven curls. This happens because the rubber band can create a tight spot where the hair is constricted, resulting in an indentation in the curl pattern. A proper perm rod set should allow for smooth transitions along the curl without any tight constrictions that would cause variability in the shape of the curls. To avoid such issues, the rubber bands should be positioned carefully to ensure that they are secure but not overly tight, maintaining consistent tension throughout the hair.