interests for a foundation supporting the University of Texas and Texas A&M University systems, publishes do-it-yourself manuals for three sizes of cattle grids with grids made of steel pipes. The manuals include schematic drawings as well as accompanying instructions. Commercial guards made of steel are also available from multiple companies. Virtual Painted lines on the road can serve as skeuomorphs of cattle grids. The light-dark pattern of lines on pavement resembles a true cattle grid to animals, and by association think they will not be able to cross. Using a virtual cattle grid is initially cheaper than a true cattle grid, but the cost of periodic re-painting may eventually exceed the initial cost of a well-built metal guard. A particular advantage of painted guards is that they are smooth to drive over; in the US, most are found on state or federal highways, rather than private roads. Why they work is unclear, but it is most likely related to the bovine visual system. Experts say that "a cow's depth perception is such that it makes little or no distinction between painted stripes on a dark background and bars over a pit." Cattle may acquire the behavior of avoiding grids over pits either from individual experience or through imitation of other cattle. However, painted grids have been reported to work with semi-wild cattle with no prior exposure to virtual grids. Cattle can sometimes defeat virtual guards. A rancher in Queensland, Australia, told a reporter that after some of his old bulls leaped a painted grid, the younger ones lost their fear of walking across. This is common; if one member of a herd discovers it can step safely on the lines, others will follow. Other incentives that lead cattle to test a virtual guard include placing food on the opposite side, or using strong driving pressure to run panicked cattle over a virtual grid. Electric Electric cattle grids use electricity to deter animals from crossing the fence line. There are different designs. One uses high-tensile wire run across the roadway, about off the ground, attached to a power source on one side. The primary advantage is cost and ease of installation. Drawbacks include the necessity of spraying vegetation with herbicides to keep weeds from shorting out the grid if there is no barrier between the wires and the ground. In addition, some low-riding vehicles can catch the wires and tear them