Solution

Essentials of a valid endorsement i) It must be on the instrument. The endorsement may be on the front side or at the back side of the instrument & if no space is left on instrument, it may be made on a separate paper affixed to it known as allonage. It should generally be in ink. ii)  It must be made by the maker or should be made by the holder of the instrument. A stranger cannot endorse it. iii) It must be signed by endorser. Full name is not important. Initials may be adequate. Thumb impression should be attested. Signature may be done on any part of instrument. A rubber stamp is not acknowledged but the designation of holder can be done by rubber stamp. iv) It may be made either by endorser only signing his name on the instrument or by any words showing a purpose to transfer or endorse the instrument to a specified person. No specific form of words is arranged for an endorsement. But intention to transfer must be there. v) It must be concluded by delivery of instrument. vi)  It must be an endorsement of the entire bill not a partial endorsement.