Simple instrument for fixing bugs in code 40 years ago. What is it ?

Question

It is small and lightweight

Answer 1

A patch, which was sticked over the holes in the punch cards ?
man the times have changed...

Answer 2

a rock to kill them with

Answer 3

Punch cards ? Yes ! 40 years ago . And punched tape too. But I ask about instrument and fixing bugs.

Answer 4

And Yes, the times have changed . But not so quickly as we think.

Answer 5

Friends, really nobody knows answer?