Internally, it's a frame with the border of a labelframe and none of the padding.
This widget appears in TclMacBag v0.11 and above.
Available options: None.
Many of the standard options for the Tile/Ttk frame can be set using [$w configure]. In practice, this is rarely necessary.
grid [::tclmacbag::boxframe .vs] -row 1 -column 2 -sticky nsew -padx 5 -pady 0