having a threaded rim that is turned on the corresponding thread on the neck of a bottle or container to close it securely
They have screw-on caps so they won't flip open.
screw-on in American English
(ˈskruːˌɑn, -ˌɔn)
adjective
1.
attached, connected, or closed by screwing onto another part of a container or receptacle
2. (of an earring)
held on the earlobe by a small screwlike post with a disk at the tip
Word origin
[1925–30; adj. use of v. phrase screw on]This word is first recorded in the period 1925–30. Other words that entered Englishat around the same time include: dropout, gimmick, payload, runout, turnaround