Is it correct grammar to write No boots allowed passed this point?

No, the grammar is incorrect. Here's why and how to fix it:

* "Passed" should be "past": "Past" is the correct preposition to use when referring to a location or point in time.

* "Allowed" should be "permitted": While "allowed" is grammatically correct, "permitted" sounds more formal and appropriate for a sign.

Here are some ways to write the sentence correctly:

* No boots permitted past this point.

* Boots are not permitted past this point.

* No boots allowed beyond this point.

You could also consider adding a reason:

* No boots permitted past this point due to [reason].