、。
In reality such a thing couldn't happen, but it looks just about right for giving a warning.
Literal
Actually [topic-は] that-kind-of thing exist [no way-わけない] [but-が], put-nail-in [for-には] just-right-seeming is.
A two-clause observation with some useful set expressions. ~わけない is a contracted/casual form of ~わけがない ('there's no way that X,' 'X cannot be the case') — marks something as impossible or unlikely. 釘を刺す is a wonderful idiom: literally 'to drive in a nail,' meaning 'to drive the point home,' 'to give someone a (stern) warning,' 'to make sure someone doesn't do something.' The image is of fixing something in place with a nail so it can't move — you're 'nailing down' the warning. ~には here marks the goal/purpose ('for the purpose of X'). ちょうどよさそう is the ~そう appearance on よい with the さ-insertion required after い-adjectives: 'looks just right.'