I had a gap where my framing meets the slab - my washer & dryer are in a closet on the other side - crickets and small spiders would enter the second it started getting colder outside.  Vinyl siding covers it on the exterior, and I could lift up the lower edge of the siding and "feel" the spot. I tried a caulking gun in the past, as well as wide caulk. The press-in-place caulk wouldn't adhere and the caulking gun was too large and awkward to use.