In The Hobbit, sacks are either empty or full of dwarves.  They do not appear after chapter 8 except as a particle in Sackville-Baggins.

• 02.072 and “a sack,
• 02.072 a sack was over his head,
• 02.075 pop! went a nasty smelly sack over his head,
• 02.080 and popped a sack right over Thorin’s head
• 02.075 With sacks
• 02.077 sticking out of sacks to tell him
• 02.078 in the bushes with sacks,” said he.
• 02.080 in sacks,
• 02.092 until at last they decided to sit on the sacks
• 02.108 to untie the sacks
• 06.046 and my stomach is wagging like an empty sack.’
• 08.050 and hoist their empty sacks