kill two birds with one stone

as best one can

In the best possible way, given one's circumstances and abilities.

as far as one knows

To the best of one's knowledge, as far as someone knows or possible information to be gathered about the topic, subject, aspect, or situation.

back to square one

Located back at the start, as after a dead end or failure.

beast with two backs

Two people united in sexual intercourse in the missionary position.

beat as one

To share the same feelings.

become one flesh

To join together in marriage; to develop a unifying bond as a result of marrying.

birds and bees

Informal education about sex.

birds of a feather

People having similar characters, backgrounds, interests, or beliefs.