Four kinds of object, four different problems, usually in the same seller's parcel.
Shirts and kit
Clean and dry, folded along existing folds, acid-free tissue over any signature so nothing rubs against it, into a sealed plastic bag against damp, then a box rather than a soft mailer so nothing presses a crease into a print or a number.
Paper — programmes, tickets, photographs
Rigid board both sides, in a sleeve, in a flat box. Small paper is lost and bent in a large box.
Equipment — bats, sticks, gloves, boots
Long and awkward. Check what your courier does with length before you quote. Pad the extremities, keep padding off any signature, and use a box rather than wrapping alone. Packing sporting goods.
Frames
Do not post glass. Take the item out and post it flat, or offer collection. Broken glass does not merely break — it damages the thing it was protecting.
Ink and light
Signatures fade, and sunlight does it fastest. Store signed items out of the light and do not leave a parcel in a hot vehicle while you run errands.
Photograph everything
The item, the packing, the sealed parcel. In a category where value rests on a claim, your own record is what settles a dispute.
Questions people ask
Can I post a framed shirt?
You can, and many sellers will not. Offer collection and let the buyer choose the risk.
Should I dry-clean a match-worn shirt?
No. Washing a match-worn item can remove part of what makes it what it is, and it must be declared if it has been done.
How do I protect a signature in transit?
Acid-free tissue directly over it, and nothing pressing on it. Pressure and heat lift ink.