1. Single line copy:

In command mode, move the cursor to the line to be copied and press yy to copy;

2. Multi-line replication:

In command mode, move the cursor to the first line to be copied, and press "nyy" to copy N lines; Where n is 1, 2, 3 ...

Paste:

In command mode, move the cursor to the line you want to paste, and then press "p" to paste.