To make identification easy there is a small groove running down the length of one tape and not the other. ‘A’ and ‘B’ tapes can be identified by looking at the non-adhesive side of the tape. ‘B’ has a groove down the middle while ‘A’ does not (fig opposite). On the sticky adhesive side it is the reverse.

The ‘A’ and ‘B’ tapes have been manufactured so that one strip of ‘A’ always aligns exactly with a ‘B’ strip of the same width (fig opposite left-hand side).

If two ‘A’ are put together they will offset and not align neatly (fig opposite right-hand side). Similarly with two ‘B’ strips put together.