Istisna'a

Istisna's:  

Istisna'a is a contract between a manufacturer/seller and a buyer under which the manufacturer/seller sells specific products after having manufactured, permissible under Islamic Shariah and Law of the country at an agreed price payable in advance or by installments withing a fixed period or on/within a fixed future date on the basis of the order placed by the buyer.

In short,

it is a contract with a manufacturer to make something.

The buyer is called: Al-mustasni'
The seller is called: Al-sani'
The goods of the contract is called: 'Al-masnoo'

Parallel Istisna's:

If the ultimate buyer does not stipulate in the contract that the seller will manufacture the products by himself, then the seller may enter into a second Istisna's contract in order to fulfil his contractual obligations in the first contract. This new contract is known as Parallel Istisna'a, whereby the obligations of the seller in the first contract are carried out.