A Lot of people are oblivious to the fact that they can make trade signs, when the find out they ask "How do i make one?" So, here's how:
Trade Sign
[Trade]
<Buying>
<Selling>


Line1: Must be '[Trade]'
Line2: What you want

Line3: What you are giving away
[Trade]
$<Cost>
<# Item>:<tot>


[Trade]
<Item>
$<Cost>:<tot>


Line2:
Should be be either:

'<amount> <item>' or '$<amount>'
[trade]
$5
10 dirt:100


[trade]
10 dirt
$5:100


Line3:
Should be be either:
'<amount> <item>:<total>' or
'$<amount>:<total>'

Total being the amount to place in the sign.
[trade]
$5:0
10 dirt:100
KHobbits


[trade]
10 dirt:0
$5:100
KHobbits


If the syntax is correct
Your name will appear on line 4.
These types of signs are typically used by players to sell items to other players.
Right clicking the sign by the owner collects the items/cash stored in the sign.
Right clicking the sign by the owner with the item being sold, will restock the sign with more items.
Anybody else right clicking the sign will buy the items being sold, if they have the 'cost' on them.
<item> can be a shortname ie 'bonemeal' or itemId '351,15'. The /itemdb command can help with this.

 

ik, it didn't really work.

 

Thanks Osr