The Alert and Action lines
In the section for cervical dilatation and fetal head descent, there are two diagonal lines labelled Alert and Action. The Alert line starts at 4 cm of cervical dilatation and it travels diagonally upwards to the point of expected full dilatation (10 cm) at the rate of 1 cm per hour. The Action line is parallel to the Alert line, and 4 hours to the right of the Alert line. These two lines are designed to warn you to take action quickly if the labour is not progressing normally.
You should refer the woman to a health centre or hospital if the marks recording cervical dilatation cross over the Alert line, i.e. indicating that cervical dilation is proceeding too slowly. (The Action line is for making decisions at health-facility level.)