An external fixation device for holding bone fragments in place includes a housing having a number of rotationally adjustable pin holders, each of which is held by a clamping member that simultaneously clamps the pin holder within an internal mounting surface of the housing and a bone pin within the pin holder. A first embodiment includes a number of pin mounting structures, each of which can include a single pin holder. A second embodiment includes one or two pin mounting structures, each of which holds a row of pin holders that is clamped in place by a single clamping member. Other embodiments are formed by fastening together a group of elements to form different housing configurations.