Avoiding Select in VBA Excel macros with variable ranges

The errors are probably being caused by the Copy and PasteSpecial lines in this block of code:

        With S
            .SL.Copy

        End With  
        With R
            .RL.PasteSpecial
        End With

Once you have Set a range variable, Excel knows which worksheet and which workbook contains that range variable. If you want to do something to the range then you do not need to include the worksheet. So, in your code, you just use

SL.Copy

RL. PasteSpecial

It is always a good idea to think if you have any code inside a loop that should be outside. In your code you Set your worksheet variables within the loop but this should be done once before the loop. Adding in the comments made to your post, your code should be changed to:

Dim S As Worksheet
Dim R As Worksheet
Set R = Sheets("Front")
Set S = Sheets("CHECK LIST")


Counter2 = 17
For Counter1 = 12 To 150

    Dim SL As Range
    Dim RL As Range
    Set SL = S.Range(S.Cells(Counter1, 1), S.Cells(Counter1, 10))
    Set RL = R.Range(R.Cells(Counter2, 1), R.Cells(Counter2, 10))

    Set curCell = Worksheets("CHECK LIST").Cells(Counter1, 6)
    Set checkCell = Worksheets("Front").Cells(3, 5)

    If curCell.Value = checkCell.Value Then

        SL.Copy
        RL.PasteSpecial

        Counter2 = Counter2 + 1
    End If
Next Counter1

The PasteSpecial method has several parameters:

.PasteSpecial Paste:=xlPasteFormats, Operation:=xlNone, SkipBlanks:=False, _
            Transpose:=False

If you are not using these, then maybe you can do a "normal" copy & paste?

SL.Copy RL