Leather boots weighing three to four pounds a pair can be replaced with Masai trail running shoes, only 1 pound 6 ounces.

In 1939, one pair of Common sails were replaced with Patent sails.

However the system failed to produce results and, after just eleven league games, the pair were sacked and replaced by Len Ashurst.

In the new version, complementary pairs of rhomboids are replaced by stacks of 10-sided arrays of atoms.

Old photographs show that a pair of matching entrances to the central 'archway' existed, but were replaced by windows and walling at an unknown date.

In some depictions of these coat of arms, the two pairs of muskets are replaced by two cannons.

The original pairs are replaced by four couples who come animatedly to life.

On the reverse, the eagle was lowered in position, and a pair of olive branches framing the eagle was replaced by stars.

Each pair is continually checked for internal consistency, and a failed pair can be replaced while its twin carries on.

Later the front pair dropped away and were replaced.