Abstract: In apparatus for coating a web, comprising a backup member having an axis, a coating head for receiving coating material and applying it to a web supported by the member for movement transverse to the axis, the head including portions defining the rear and bottom walls of a coating chamber; and a dike system for confining the coating material in the chamber, the system comprising a pair of inboard dikes spaced apart along the axis, each inboard dike having a control surface shaped to conform to the backup member along a margin of the web and having an operating position in which the control surface is spaced from the backup member sufficiently to allow the coating material to bleed between the control surface and the web to coat the margin, the control surface in the operating position being sufficiently close to the backup member to confine most of the coating material to between the inboard dikes; and a pair of outboard dikes respectively spaced outwardly from the inboard dikes along the axis, the outboard