In practice
Side pockets are set up under the fund’s offering documents, usually when an asset loses liquidity or a private holding is hard to price. Each investor’s share is fixed at the time of the transfer, so later subscribers do not participate. Fees on the pocket are often charged only on realization. A side pocket differs from a gate, which limits redemptions across the whole fund.
An example
Round numbers, not a real fundSay a hedge fund holds $20 million of assets it cannot sell. It moves them into a side pocket. Investors who redeem get cash for the rest and keep their share of the pocket.
Why it matters
It protects investors who stay from being left with the illiquid assets, and it traps those who wanted to leave.
A definition, not advice; where usage varies the entry says so. Something wrong? Tell the desk.