Never carry two faces under one hat.

Understand the thought

Meaning in plain English

Do not present conflicting positions to different people in order to mislead them. The saying criticises duplicity, while allowing honest changes of mind and appropriate differences in how you communicate.

What the words are saying

Two faces under one hat makes one person appear to have incompatible outward identities. Figuratively, the person may tell each audience what it wants to hear while concealing a contradiction that matters. The criticism concerns misleading conduct rather than the mere fact that people speak differently in different settings. Privacy, tact or a genuine revised judgement do not automatically amount to duplicity. The useful question is whether others are being given a materially false impression of the same commitment or position. Consistency can include acknowledging a change openly instead of pretending that contradictory assurances can both be kept.

Everyday example

A coordinator tells both teams the same limit on room availability rather than promising each exclusive use and hoping they will not compare arrangements.

When to use it

Use it when contradictory assurances are being concealed to mislead different audiences.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.