A positioning apparatus includes a first portion (123) having a first opening (125) for alignment with a port entry point. A second portion (127) is positionable for alignment with the first opening from a plurality of different positions. An actuation mechanism (142) is coupled to at least one of the first portion and the second portion to set relative positions of the first and second portions to permit a tool axis formed between the first and second portions to be aligned through the first opening such that a tool (104) provided on the tool axis would include a known position and orientation.