What is "to flush a joints"

Flush \Flush\, v. t.

1. To cause to be full; to flood; to overflow; to overwhelm with water; as, to flush the meadows; to flood for the purpose of cleaning; as, to flush a sewer.

2. To cause the blood to rush into (the face); to put to the blush, or to cause to glow with excitement.

   Nor flush with shame the passing virgin's cheek.
   --Gay.

   Sudden a thought came like a full-blown rose, Flushing his brow.
   --Keats.

3. To make suddenly or temporarily red or rosy, as if suffused with blood.

   How faintly flushed. how phantom fair, Was Monte Rosa, hanging there!
   --Tennyson.

4. To excite; to animate; to stir.

   Such things as can only feed his pride and flush his ambition.
   --South.

5. To cause to start, as a hunter a bird.
   --Nares.

6. To cause to flow; to draw water from, or pour it over or through (a pond, meadow, sewer, etc.); to cleanse by means of a rush of water.

   To flush a joints (Masonry), to fill them in; to point the level; to make them flush.