I do not recommend using glue traps for catching rats, because rats can escape from these type of traps, and they may even chew off one of their limbs in order to get free.
There is also controversy as to whether glue traps are a humane method for killing rats and other rodents, because it takes a long time for the rat to die an agonizing death after it has been caught in one of these traps.
Rather than glue traps, I would recommend that you utilize a spring-loaded trap that will kill the rat very quickly, or better yet, use a rat zapper, which is a modern version of the rat trap that uses send electric current to kill a rat.
Not only more humane, these types of traps are much more effective that killing rats and eradicating rat infestations.