Abstract: A borehole tool member has an elongated slot with a surrounding seal for engaging the wall of the borehole for sampling fluid from the subsurface formations. A passage extends from the slot through a portion of the tool member to an upper opening which is connected to a conduit that extends to the surface. The seal surrounding the slot is forced against the borehole wall by two pistons located in two cylindrical chambers formed into the tool member. The pistons are actuated for movement outward of the tool member by fluid under pressure injected from the surface by way of a pressure control line extending from the surface to a second passage formed in the tool member and which extends to the two cylindrical chambers. Springs are provided for returning the pistons inward upon release of the fluid pressure in the cylindrical chambers.