Abstract: For installing a screen of flexible material in the soil, a trench is dug in the soil and the screen is fed into the trench. To provide a method in which the sagging or dragging along of the screen by the collapsing soil is avoided in a simple manner without use having to be made of an additional machine or the like, facilities are added to the screen itself to prevent its sagging into the still unfilled trench. The facilities may consist of a wire strung through the top edge of the screen and held under a certain tension, a strip which is bonded along the top edge of the screen and which is held under a certain tension, or an inflatable sleeve fitted to the top edge of the screen. Further it is possible that the entire screen is constructed in a sleeve-like form and is filled with gas, liquid or substance.

Abstract: A sheet of material is laid in the ground by digging a trench in the ground by means of a trench digger and unwinding the sheet of material from a stock roll above ground level, passing it into the trench in a downward direction and diverting it in a direction essentially parallel to ground level. In order for the protective housing which is attached downstream of the trench digger and has to keep the trench open over its length not to be designed too long the sheet of material is passed into the trench folded double and is unfolded via three return rollers or rods or flanges, and passed in the unfolded state in an approximately vertical plane in the horizontal direction.