Endoscopic endonasal skull base surgery is performed by inserting up to three surgical instruments into nostrils. It is difficult to install three haptic interfaces representing each instrument around the narrow nostril models without interference problem for training the surgery. Parallelogram mechanism for solving the interference problem and a method to implement insertion movement using the parallelogram mechanism are proposed in this paper. Two linear guides are installed at links to keep parallelogram for measuring movement of the haptic interfaces and transmitting haptic feedback to the operator exactly. Analysis of the minimum length of the linear guides to satisfy the workspace of the haptic interfaces is conducted. It is possible to insert the handle of the haptic interfaces while avoiding of the interference by using the parallelogram mechanism with two linear guides.