Shield

Shielding is when you just deposit your Sol into the pool, allowing you to withdraw, send, or let it sit for however long you want. The process is the exact same as a private send, the only two differences are:

1) You set the recipient address to yourself

and

2) You only ever have to do it once, there's no need to "top up" because it isn't being sent anywhere.

However, if you have shielded sol and try to do a private send for more than that balance, you will have to top up again.