Rectangular nets hang from string or frames and are more spacious. Polyester netting is the most common fabric for nets because it absorbs little water. A sheeting border prevents tearing when the net is tucked under a mat, and at the top of a conical net, sheeting reinforces the weight-bearing apex. Unfortunately, sheeting tends to absorb more liquid than netting. Therefore, when a reinforced net is dipped, a large and usually unknown fraction of the insecticide is absorbed by sheeting tops and borders, where it is presumably much less effective.
Durability is an important determinant of net cost, a strong net being a more attractive purchase.
In other words, more expensive nets cost less in the long-run. When insecticides are handled, stored, diluted and used correctly, they are not harmful to humans. However, they can harm fish and bees, so waste insecticide should be poured into a pit latrine, not a river or pond. Insecticides can also be purchased in several different-sized containers. Bulk quantities are often cheaper, but containers holding between one and five liters may be easier to use.