Certificates make it easier to trade large quantities of items between players. You may exchange your items/ores/bars for certificates, which are light and easy to carry. You may carry as many of these certificates as you want at once, unlike items that take inventory slots. 5 ores gets you one certificate. You also may redeem the certificates at the same place where you get them, to get back the items/ores/bars. The advantage of doing this is you can trade large amounts with other players quickly and safely. They stack like arrows or runes or gold pieces, so you can carry as many as you like.
For every 5 of any of these items you will receive one certificate that looks like this in place of the item
Ore Exchange Stall
This stall is
located in Draynor village right below the Draynor Mansion.
Ores you may exchange:
Iron
Coal
Mithril
Gold
Silver
Bar Exchange Stall
This stall is located in Draynor village right below the Draynor Mansion.
Bars you may exchange:
Iron
Steel
Mithril
Gold
Silver
Fish Exchange Stall
This stall is
located in Draynor village right below Draynor Mansion.
Fish you may exchange:
Raw Lobster
Lobster
Raw Swordfish
Swordfish
Member Fish Exchange Stall
This stall is located in Catherby
Fish you may exchange:
Raw Bass
Bass
Raw Shark
Shark
Potion Exchange Stall
This stall is
located in Yanille in the building across from the magic guild.
Items you may exchange:
super attack potions
super defence potions
super strength potions
prayer potions
dragon bones
limpwurt roots
Log Exchange Stall
This stall is located in
North Ardougne outside wall in a small hut. There is a man called Chuck.