The general sign for pound can be used to mean several "weight" related concepts.
POUND / WEIGH / TON:
Both hands form "H" shapes. The dominant "H" rocks back and forth on top of the
non-dominant "H" in a quick double movement.
The non-dominant hand doesn't move during this sign.




Here is a view of that sign from an angle:

POUND: (alternate method)
When you are specifically talking about "pounds" you can use either the
"pound/weigh/ton" sign above, or you can spell the letters "L" and "B."
When you use the fingerspelled version you do not add an "S" to
indicate the plural "pounds." Instead you pluralize this concept by stating
the number of pounds, for example: 15 LB.
LB:


Notes:
If you mean pound as in "dog
pound" you should not use the above signs for
"POUND"-(weight/weigh/ton).
Instead you should spell "pound."





If you mean "pound" as in "the boxer pounded on
his opponent" or the cook pounded on the chicken you should use a
mimed version of HIT wherein you throw a
few mock punches (using a serious, focused facial expression) or you
mime hitting a (dead, plucked, and cleaned) chicken with a food
mallet.
See: OUNCE
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American Sign Language (ASL) online at American Sign Language University ™
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