Abstract: The invention relates to apparatus and methods and kits for constructing walls such as diaphragm walls comprising one or more panels and walls so constructed. In particular the invention relates to apparatus, methods and diaphragm walls having a guideway along a height of a first wall of a pane). More particularly, the invention relates to an apparatus for constructing a diaphragm wall comprising: a guideway tube along a height of a first wall of a first concrete panel; a sacrificial wall element in the guideway tube that extends along the tube and about a portion of a periphery of the tube; a cutting mechanism for cutting along the height of a first wall of the first concrete panel, the cutting mechanism being arranged to cut along the height of the wall of the first concrete panel and along the sacrificial wall element of the guideway tube so as to cut away at least part of the sacrificial wall element of the guideway tube along at least part of the height of the first wall.