Sister Block

(Naut.) a tackle block having two sheaves, one above the other.

See also: Sister

References in periodicals archive ?
There is a sister block that is exactly the same design to Lakanal House and the residents there haven't been able to sleep since Friday night because, until we know the cause, they can't be sure the same thing won't happen there.
JAMMED: Fire-door CHILLING: Warning sign at flats ALARM: Only exit at Lakanal's sister block
Mr Tarling examined Marie Curie house, the sister block to Lakanal House, a few days after the fire.