A coupler for to which a shaft is attachable is provided. includes a base. The base is formed with an upper side and an lower side. The lower side is substantially a flat planar surface. Means are provided for mounting the base on a curved surface. A preferred means is one or more ball washer assemblies. In addition, the present invention includes a tub that is adjustably connectable to the base. A plug is provided that is repositionably attachable to the tub. In addition, a neck is provided. The neck is insertable into the plug. The neck also is formed to support a shaft. The invention includes a clevis mechanism that is slidably and demountably engageable with both the plug and the neck.