Trestle with Deck Girder Bridge Kit HO Scale 3147Walthers Cornerstone Trestle with Deck Girder Bridge Kit 15 1 2 x 4 x 4" 38. 7 x 10 x 10cm HO Scale Walthers Cornerstone #: 933 3147 From the earliest days of railroading, the civil engineers who laid out the line faced low spots, streams and other obstacles that had to be crossed. This required some sort of bridge, and in many cases, a trestle was a cheaper, faster option. Trestles consist of a series of piers, called bents, which support the track.