When the central bank needs to absorb excess liquidity from the financial system to prevent short-term money market rates from falling below its target floor, it executes Reverse Repos. [1]
The Reverse Repo Liquidity Absorption Channel
  Operation Type |   Central Bank Asset Movement     |   Interbank Liquidity Impact
-----------------+-----------------------------------+---------------------------------------
  Standard Repo  | Buys bonds; injects cash reserves | Expands short-term reserve availability
  Reverse Repo   | Sells bonds; drains cash reserves | Shrinks excess interbank money pools

In the United States, the Federal Reserve’s Overnight Reverse Repurchase Facility (ON RRP) allows a broad network of primary dealers, money market funds, and government-sponsored enterprises to park excess cash overnight with the Fed in exchange for US Treasury collateral, establishing a hard floor for short-term dollar interest rates. [1]

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