Abstract: The invention relates to a field liner for protecting a timber pole against subsoil decay. The field liner includes a sleeve, that can be loosely located on a pole for covering the region of the pole to be protected, and a covering sheet that is secured to and extends from the sleeve in a configuration in which, with the sleeve located on a pole, the covering sheet can be tightly drawn and held around the sleeve for holding the sleeve tightly against the pole. The sleeve includes at least a flexible, liquid impermeable, non-biodegradable, synthetic plastics film material layer, whereas the covering sheet is formed of a flexible, non-biodegradable, woven synthetic plastics sheet material.