The kikai-jyakuri-kanna (機械決り鉋 or 機械作里鉋) is a handy style of plane for cutting continuous grooves of widths from about 3mm up to 15mm. Max cutting depth is about 12mm . It is similar to the western grooving planes in function (cuts a rectangular groove), but not in construction. These are (were) typically used for cutting the grooves required to insert thin panels or glass into shoji doors or similar items. It is a special purpose plane that has limitations. The router has really replaced these planes but these are a lot more pleasant to work with and are still available new and used.