Select and delete contents below diagonal of cell array

If your (square array) is 6x6 staring from A1, then maybe this.
It deletes the below diagonal but doesn't select.
Do you really want to select? If so, why? Selecting isn't usually useful.

Sub below_diag()
Const n As Long = 6
With Range("A1").Resize(n, n)
    a = .Value
    For i = 1 To n
        For j = 1 To i - 1
             a(i, j) = vbNullString
        Next j
    Next i
Range("A1").Resize(n, n) = a
End With
End Sub