sliver box

10 LETTERS · STARTS WITH S

sliver box is a valid 10-letter word worth 21 points in Scrabble and 24 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

S1L1I1V4E1R1B3O1X8

1 + 1 + 1 + 4 + 1 + 1 + 0 + 3 + 1 + 8 =21 PTS

DOUBLE WORD → 42TRIPLE WORD → 63

MEANING

What does sliver box mean?