Because a casualty must be raised vertically out of a manhole, shaft or tank opening.

Without a point directly above the opening, a vertical lift is not possible.

Dragging someone sideways out of an opening is not practical or safe.

The anchor also positions the fall arrest device correctly for someone entering.

Structures rarely provide a suitable point directly above an opening.

That is why portable overhead anchors exist as a product category.

Unrestrained legs - the load from a winch under a casualty acts to push them apart.

Chains, straps or a base ring restrain them and are not optional.

A tripod rigged without restraint can collapse under exactly the load it was set up for.

Uneven leg adjustment also moves the head off the opening.

Soft or sloping ground introduces its own stability problems.

Checking restraint and leg length before loading takes seconds and prevents the failure.

Where the surroundings cannot take a tripod - against a wall, over the side of a vessel, or in an awkward position.

A davit arm can be offset from its base, reaching over an opening its base cannot straddle.

Bases may be portable, socketed into a floor mount, or fixed.

Sockets built into structures suit locations where entry is routine.

Davits also suit openings in walls and vertical surfaces.

Tripods remain simpler and faster where the opening is in open ground.

Considerably - geometry is part of the rated capacity rather than incidental to it.

Extending a davit arm further from its base reduces the permitted load.

Setting tripod legs at a different height changes the geometry the rating assumed.

Manufacturers publish the permitted configurations and their ratings.

Rigging outside those configurations is not covered by the rating.

The published data should be at the job rather than in an office.

The strictest ones, because this is lifting equipment used to lift people.

Most jurisdictions impose shorter examination intervals for person-lifting than for load-lifting.

Thorough examination is by a competent person and is recorded.

Pre-use inspection by the user is required in addition.

Records travel with the equipment and are checked before use.

Equipment hired in should arrive with current certification, and verifying it is part of accepting it.

Retrieval winches and fall arrest blocks, on separate lines and separate mounting points.

The winch raises and lowers; the fall arrest block catches a fall.

Mounting brackets are specific to the tripod or davit model.

Mixing equipment between manufacturers is not covered by either certification.

Pulleys and rope guides route the lines over the head casting.

Buying the anchor, winch and fall arrest device as a matched system removes compatibility questions.

Tripods in minutes; davits depend on whether a socket is already installed.

That speed matters because rescue time is measured in minutes.

Pre-installed sockets make davit deployment very fast at locations used regularly.

Equipment that has to be worked out on the day does not meet the requirement.

Rigging should be rehearsed rather than read from instructions during an incident.

For planned entries, rigging before entry rather than after an incident is the expectation.