Under the Negotiable Instruments Act, 1881, how is a negotiable instrument payable to order negotiated?

Section 48 of the Negotiable Instruments Act, 1881 provides that an instrument payable to order is negotiated by the holder indorsing and delivering it. Delivery alone negotiates an instrument payable to bearer under section 47. An indorsement does not negotiate the instrument until it is delivered, and no registration is required.