The number 3 hinge is used to house the roller and join the third panel to the fourth panel from the ground, it is also generally used on all internal vertical frame sections. The easiest way to confirm what number hinge you require is by looking at the number stamped on your existing hinge as these are generally stamped 1-7 with 1-3 being the most common. Replacement hinge to suit earlier Steel-Line sectional garage doors. These hinges are embossed with a number 1, 2, 3 or 4 according to which panel they came from for the immediate left and right hinges. There are also middle hinges which may be embossed with very small numbers but are not relevant to the hinge. Dimensions: 160mm long x 55mm wide Please select carefully as hinges look the same initially however the hole centers for the roller shaft vary by 5-6mm between each panel so fitting the incorrect hinge will cause your door to bind or scrape along the face.