Abstract: A tool (7) for sampling or extracting the contents of a pit (4) is suspended from a cable (8) passing through a narrow opening (3) in a slab (2) covering the pit. A crosspiece (13) hooked to guide cables (11) which converge on it makes it possible to displace the lifting cable (8) under the slab (2) according to different movements imposed by winches (10). Thus it is possible to move the tool (7) to the desired point with great precision and without having to descend into the pit (4).

Abstract: The invention relates to a process for blind placement of a cable under a slab (14) such as a slab closing off a storage silo for the storage of noxious products, between two openings (24, 34). A target (42) is lowered through one (24) of the openings and a gun (38) is lowered through the other opening (34). The target (42) and the gun (38) are rotated to face each other and a projectile such as a harpoon (40) is then fired with a gun towards the target, after attaching a hemp rope (44) to the harpoon. After lifting the target (42) above the slab (14) and disconnecting the harpoon (40), the cable is attached to the other end of the hemp rope and the hemp rope is pulled through the opening (24) until the cable is put into place.