From Security Gate Page:

Whether you are a door dealer or an architect you will find timely information about our side folding and rolling security closure and grille products. We have security solutions for all your storefront entrances and counter needs. Information is available on the choice of rolling grilles and closures or side folding grilles and closures, door styles and installation options.

DC Series Gates are designed for maximum durability and security. Double steel channels are riveted together to form each vertical member and connected with double rows of steel lattice bars traveling on nylon bearings and washers to operate with a minimum of effort. Leading and trailing edges are steel box shaped sections. DC series gates can be manufactured to almost any size.

LT Series Gates are performance-designed to meet the needs of the most cost-conscious buyer. Quality construction is achieved by the use of diagonal steel lattice channels in a diamond pattern riveted together through nylon spacers for light weight and smooth operation. LT series gates are normally limited to 26' wide with a standard height of 6'-6”. 

EG Series Gates are value engineered to offer a balance between security and economy. Vertical members are single steel channels, alternating with steel flat bars, and connected with single rows of steel lattice bars traveling on formed steel glides for carefree operation. EG series gates are commonly provided up to 30' wide and 12' high, but even larger sizes may be available for some models.