If you place your shares into sell orders the shorters cannot borrow them to short with. In effect, you remove your shares from the shorters pool of which they could potentially borrow from.
When you place your shares into a sell order you in effect reserve them, they are 'pending sale', they cannot be "borrowed" because they have to be ready for your sale if and when the pps pops up to your ask.
If enough people knew 0f this and actually kept their shares 'reserved' inside of sell orders, the shorters would have less effect and/or control of the stocks negative movements.