For the record, according to National Geographic, the U.S.-Mexico border is 1,954 miles long (or 3,145 km).
So, yeah, in case you're wondering, putting up a 316 mile wall on a 1,954 mile border is kind of like putting in a pool and only filling it up with enough water to get your feet and ankles wet. At the end of the day, you don't solve your problem ... and you're kind of left hanging.
But, but ... that's alright, since your neighbor's going to pay for the pool anyways, right? Right!?