I have a workbook with about 50 sheets. I need to copy all rows starting
from row 18 down from all sheets to one sheet called summary.

Any suggestions other than going out of my mind and doing it manually?

Thanks

Assuming your data is:
1) in a big block (no gaps)
2) starts at row 18 column 1
3) has at least 2 bits of data on each page (the end(xldown) will not find
the end of the data otherwise)

then the following should do the trick

Sub copyEighteen()
Dim sht As Worksheet
Dim rng As Range

With Worksheets("Summary")
For Each sht In ThisWorkbook.Worksheets
'Process all but the summary sheet
If Not sht.Name = "Summary" Then
If Not IsEmpty(sht.Cells(18, 1)) Then
Set rng = Range(sht.Cells(18, 1), sht.Cells(18,
1).End(xlDown).End(xlToRight))
Range(.Cells(60000, 1).End(xlUp).Offset(1, 0),
..Cells(60000, 1).End(xlUp).Offset(rng.Rows.Count, rng.Columns.Count -
1)).Value = rng.Value
End If
End If
Next
End With
End Sub