When typing in short hand assembled machine code (not assembly language!) into a single board computer (like the Sintel SBC-85, which was popular in Israel and featured an Intel 8085), it was customary to keep your patch space inside your code, by inserting NOPs every 10 or 20 instructions.
The only way of editing a program you'd keyed into memory was to overwrite memory locations. The monitor had no insert, partially due to difficulty of implementation, but mostly because inserting makes no sense inside machine code. After you insert, all jumps (and some branches) need to be adjusted; a simple scan of memory cannot do the trick, as it has no way of distinguishing code from data (and generally that distinction does not exist).
Instead, you'd overwrite your old code with your new code. If the new code was longer than the old code, hopefully you'd still fit into the next block of NOPs and save lots of keying. If the new code was shorter, things were even easier -- just pad the remainder with NOPs.