A friend ask me about 10 days rule after H1b being expired, here it is:
(Text of subsection (h)(13)(i)(A) effective Oct.1, 2002)
(A) A benefidciary may be admitted to the United States for the valideity period of the petition, plus a period of up to 10 days beforee the validity period begins and 10 days after the validity period ends. The beneficiary may not work except durign the validity perod of te petition