Hydraulic Sleeve with Early Release Prevention

A downhole window tool includes an internal sleeve slidably received within an outer housing. The sleeve and outer housing may have windows that selectively align or the sleeve may move out of alignment with the window to allow fluid passage through a window. Sleeve movement within the housing is controlled by inserting a dart or plug in the interior of the sleeve to allow pressure to act on the plug or dart to move the sleeve a set amount to open the lateral window. A shear pin or other device may be used to control the amount of force necessary to open the window and further ensure unintended opening of the lateral window. The use of the removable dart or plug both prevents unintentional forces from opening the window and increases the amount of throughput through the sleeve as compared to when valve structure is installed within the tool.