This begins to get more difficult now but 2Bs can bring direct pressure to bear and must force the King into a corner to mate.
From the following position with black to move
1. ... Ke7
Once again the king wants to get in the centre where it cannot be mated
2. Bf4 .. Ke6;
3. Bd3 .. Kf6;
4. Be4
With this move the King cannot approach the B pair and is already restricted to only 19 squares
4. ... Ke6;
5. Kd2
This King must now come up in support
5. ... Kd7;
6. Kd3 .. Ke6;
7. Kd4 .. Kf6;
8. Kd5 .. Ke7;
9. Be5 .. Kd7;
10. Bf5+ .. Ke7;
11. Bb2 .. Ke8;
12. Ke6 .. Kd8;
13. Kd6 .. Ke8;
14. Bg6+ .. Kd8;
15. Be5 .. Kc8;
16. Kc6 .. Kd8;
17. Bf6+ .. Kc8;
Now we are driving the king towards the corner where it must be for mate to be delivered
18. Bf5+ .. Kb8;
19. Kb6 .. Ka8;
20. Bc3 .. Kb8;
21. Be5+ .. Ka8;
22. Be4++
This may not be the quickest way but it shows the principles of how it is done. Mate can be delivered in either corner.