In the Helsingborg area the line was reinforced with a second line of rear-facing machine gun bunkers. As a further improvement there was also added a line of shelters to protect personnel from aerial bombing and artillery bombardment. There were two types of shelter designs (called SK24 and SK48), designed to provide protection for either 24 or 48 soldiers. This line stretches from Ystad to the north of Helsingborg, and consists of about 70 shelters.