Choose a tack box you can lift and clean
Judge a box when it is filled, carried and opened in the space where you will use it, not only by its advertised capacity.
Start with the contents you carry
Lay out the equipment that genuinely travels with you before choosing a box. A large empty box looks useful, but it invites extra items until it becomes awkward to lift. Group the contents by task and remove duplicates that have no clear purpose. Measure the longest or bulkiest item rather than relying on a litre capacity that says little about the internal shape.
Consider the empty weight as well as the filled weight. A rigid case may protect its contents well but add substantially to the load. Try the handle position and balance with a realistic load where the retailer permits it. If lifting the box into the vehicle is uncomfortable, splitting the kit into two manageable containers may be more useful than choosing an even larger case with wheels.
Check the opening and the small parts
Look at how far the lid opens and whether it stays safely in that position on the intended surface. A removable tray should be easy to lift without spilling its contents. Check that hinges, corners and latches do not catch fingers or snag nearby fabric. Ask whether replacement catches or handles are available if the box is intended for frequent use.
Keep pointed tools and small loose components in suitable positions so they can be found without rummaging. Store liquids upright according to their labels and separately where a leak could damage the rest of the contents. A complicated arrangement of tiny compartments is not an advantage if ordinary brushes no longer fit or the bottom cannot be cleaned.
Make cleaning part of the choice
Read the care instructions for the complete box, including its lining and fittings. Wipe-clean construction does not necessarily mean the case can be soaked or hosed out. LeMieux's hard-shell grooming box is one example with a wipe-clean instruction. Follow the directions for the actual product and allow it to dry before returning clean equipment to it.
Finally, decide where the box will sit at the yard and in the vehicle. It should not block a route or be left where a horse can knock it over. Do not stand or sit on it unless the manufacturer specifically designed it for that use. A portable box earns its space by making equipment easier to carry, identify and clean. If it becomes too heavy to move or too crowded to empty, reduce the contents before blaming the lack of another compartment.
Reading & references