RewriteRule of .htaccess, with slash at the end

I have two kinds of links on my site: first are finishing with .html, and second that are finishing with / (with slash, in a case that filename is not finishing with .html).

Cause of some rewriting rules, in a case that file is not .html, and if is added / at the end, URL is not properly rewritten.

Like:

It is ok with link: http://mysite.com/cars/fast-cars

But not ok with link: http://mysite.com/cars/fast-cars/

So, what I need is when URL is finishing with / and not with (.html/), to be redirected to same page, without /, or in this case:

http://mysite.com/cars/fast-cars/ to be redirected to http://mysite.com/cars/fast-cars.

Hope I was clear, and that you can help me with that htaccess rule. Thank you in advance.

UPDATED: i did found part of solution here: .htaccess with or without slash.

but, also, my rule should not be valid for some subdirectories (like directory admin, orders, etc). can it be defined also with same rule?

UPDATE 2: I have rules like:

RewriteRule ^c开发者_StackOverflow社区ars/fast-cars$ /seopage.php?marker=fast-cars$1

Also, tryed with rule that works:

RewriteRule (.*)/$ $1 [L,R=301]

But that rule have to be bypassed for some directories (ie. admin, orders, etc.).

You can do this in few ways (choose the one that works best for you).

1) Remove trailing slash / for non-existing files and folders:

# remove trailing slash for non-existing files and folders
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ $1 [L,R=301]

2) Remove trailing slash / with exceptions

# remove trailing slash except some folders
RewriteCond %{REQUEST_URI} !^/(admin|orders)
RewriteRule ^(.*)/$ $1 [L,R=301]

3) You can even combine it together (which can be too much):

RewriteCond %{REQUEST_URI} !^/(admin|orders)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ $1 [L,R=301]

Also, consider adding this directive somewhere at the top -- documentation:

DirectorySlash Off