Keyboards and other input devices are provided with at least one flexible layer that extends over or under the keycaps. The flexible layer spans interkey spaces and lies between inner and outer keycaps. The flexible layer prevents intrusion of invasive material to the keyboard mechanisms and simplifies the appearance of the keyboard area. Some flexible layers help align keycaps by connecting inner and outer keycaps or by providing a mechanical connection interface for the keycaps. Some membranes used in the flexible layer have a layered or composite construction that increases durability and tear resistance by attaching or infusing a mesh material or other tough material to a less durable, elastic material.