So you’ve just defeated the Goblin Chieftan Bik-Dik of the Skinworms Tribe in a glorious fight that went back and forth, and you’ve now begun looting his smelly, beaten corpse. Bik-Dik was wearing a Half Plate armor set, which is better than your Chain Shirt. Naturally, you want to equip that Half Plate for that sweet 15 AC. But hold your horses for a minute there, skip. You’re a Half-Orc Fighter, your size is medium. Bik-Dik is a Goblin, and Goblins are small, you probably couldn’t even fit your thigh down into that Half Plate (you might want to reconsider eating all those sweet-rolls earlier). However, fret not, brave adventurer!
If you find a blacksmith or an armorer, he or she will be able to re-size the armor for you, it’ll cost you a bit, but significantly less than buying new stuff. Oh, and you might want to put that chain shirt back on first… Those nips could cut steel, my friend.
The same goes if you want to snatch some equipment off of something bigger, say a Hill Giant. What is a Dagger to a Hill Giant is a Greatsword to a Medium character, so maybe your Gnome Paladin should not be waving that thing around in public. Gear like this can’t, obviously, be resized, however, you may find collectors and other weird folk, that’ll pay you handsomely for giving them the big one.
Now, go on out there, and do adventuring and stuff… And don’t forget to wash your hands and get your mind out of the gutter.