Flat racks and open tops are the two workhorse special containers for cargo that won’t fit through a standard door. An open top is a normal container with a removable tarpaulin roof, used for tall cargo loaded by crane from above. A flat rack is essentially a steel platform with end walls, used for over-width, over-height, or extremely heavy pieces that must be lifted or rolled on from the side. If your cargo exceeds the box in more than one dimension, the flat rack usually wins.
Open top containers: top loading, standard width
Open tops (20′ and 40′) keep standard container walls and floor, so cargo stays protected on all sides. They suit machinery, glass, timber, and steel coils that are too tall for door loading but fit within standard width. Cargo higher than the container walls travels “in-gauge or over-height” with the tarp off, which the shipping line prices as an out-of-gauge (OOG) move because the slot above cannot be used.
Flat racks: for oversized and heavy pieces
Flat racks come with fixed or collapsible end walls and no sides or roof. Load limits are impressive — 40′ flat racks commonly carry 40–45 tons concentrated on the platform. Boats, transformers, construction equipment, and project cargo ride on flat racks, lashed and secured to rated lashing points. Over-width and over-height pieces are billed OOG, and extremely wide loads may require the line to block adjacent slots.
Cost, securing, and surveys
Both equipment types cost more than dry boxes: special-equipment surcharges, OOG fees for anything outside the envelope, and lashing/securing labor. Flat rack cargo usually needs a lashing plan and sometimes a marine surveyor’s approval — standard practice in project cargo logistics. Proper dunnage, chains, and edge protection are the shipper’s responsibility unless your 3PL takes it on.
The trucking leg: permits and equipment
Out-of-gauge on the water usually means oversize on the road. Over-width flat racks move under Florida overweight and oversize permits, sometimes with escorts, and need step-deck or lowboy-style chassis handling. Our guide to heavy haul trucking in Florida covers the permit thresholds and lead times to build into your schedule.
OOG moves through Miami with Go Freight
Go Freight handles flat rack and open top drayage at PortMiami and Port Everglades with owned trucks, specialized chassis, and riggers for lashing and securing — coordinated end-to-end by our AI-dispatched drayage team.
Frequently asked questions
When should I use a flat rack instead of an open top?
Use a flat rack when cargo is over-width, must be loaded from the side, or exceeds the weight a standard floor can take. Use an open top when cargo fits standard width and simply needs crane loading from above.
What does out-of-gauge (OOG) mean?
OOG means cargo extends beyond the standard container envelope in height, width, or length. Lines charge extra because the overhanging dimensions consume adjacent vessel slots that can’t be sold.
Do flat rack shipments need special permits for trucking?
Often, yes. If the loaded dimensions exceed Florida’s legal limits — 8’6″ wide or 13’6″ high on most roads — the drayage leg requires state oversize permits and possibly escort vehicles.
Moving out-of-gauge cargo through South Florida? Request a project quote or call (786) 445-0150.