Rather than existing as a computer input device with a rigid shape, a predetermined selection of controls and a fixed layout, a malleable control structure is made up of a set of controls that can be freely arranged on control areas. The structure is physically adaptable by users during operation: control areas and controls can be introduced, organized and removed to suit interaction requirements and personal preference.We present an implementation of a malleable control structure called VoodooIO. Our design contributes a novel material -- the network substrate - that can be used to transform everyday surfaces into control areas, and the concept of implementing basic control units (such as buttons, sliders or dials) as ad hoc network nodes.VoodooIO does not constitute an application interface in itself. Like any input device, it only becomes concrete as an interface component in the context of a particular application. We introduce the concept of softwiring as a collection of techniques and practices that allow users to benefit from malleable control interfaces in a number of concrete scenarios of use.