[jQuery] Can't Add a checked=checked Attribute to Input tag

[jQuery] Can't Add a checked=checked Attribute to Input tag


Very simply, I want this function to attach the attribute
checked=checked to the input with the id=ext[agree]Y.
The following code does not do this and I'm not sure why...
$("ext\\[agree\\]Y").attr("checked", "checked");
Any help or ideas is greatly appreciated. Other ways of doing this
would be great as well. I just want to add this upon form submission.
Thanks.