Throughout this work, our main concern will be elastic collisions with equal mass. We use the well-known "N/D" method in order to investigate the resonance behavior of the partial-wave amplitude. We replace the whole left hand cut of the amplitude by two input-poles constrained to satisfy a threshold requirement. We derive the necessary and sufficient conditions for resonance, and see that a narrow resonance is indeed possible. Since the dynamics of crossed channels gives rise to the driving force which makes the reaction in the direct channel possible, we discuss the mechanism and formalism of the crossed channels. Using these ideas, we adjust the position of the input-poles to represent a crossed channel resonance. As a result, we show that "simple" bootstrap dynamics fails to prove the existence of the rho-meson Produced by ㅠㅠ resonance.