Wire meshes such as the one in the photograph are commonplace in modern houses. They are the easiest and cheapest way of safeguarding from mosquitoes while simultaneously keeping the air circulating.
Although it may not seem possible, different meshes actually have different designs and arrangements of metal wires. From afar the gaps between the wires all look like perfect squares, but closer inspection reveals that this is not the case. The mesh in this photograph, for example, has a grid-like configuration with the gaps in the shape of trapeziums (in case you don’t know, a trapezium is a quadrilateral with only one pair of parallel sides). The horizontal wires in the picture are parallel to each other, but the vertical ones aren’t. The vertical wires actually turn a little at every intersection with a horizontal wire, giving a zig-zag effect.
Another interesting thing that you may actually have observed yourself is that photographs of fine wire meshes and nets often produce strange patterns when you zoom in or out. These patterns are known as Moire patterns. To see the Moire patterns changing in this photo, click here, then here, and then here. You should notice that the patterns on the mesh change each time. Nothing is being altered about the image: it is the same photograph. The only difference in each case is the image size. Because computer screens are made of pixels, the patterns appear different in different resolutions. If possible, another thing you can try is clicking the same link on two different devices (say a laptop and a smartphone). You should see that the pattern looks different in each case, even though the image is exactly same. You can read more about them here.
(Submitted to the Daily Post’s Weekly Photo Challenge: “Grid“)