Technical Drawing Standards: Leader Lines.

A leader line is a line that establishes a connection between a graphical representation of an item and some text. A leader points to a bit of our drawing and says:
‘Oi – Look Here’ and ‘Read This!’.

The leader line itself should be a continuous Thin line (see this post on Linetype Definitions). A leader line also has a terminator and some text. A leader line may have a reference line under the text.

The British technical drawing standards give us four different types of terminators to use with our leader lines.

BS ISO Leader Lines

An arrow terminator is used to point to an edge of an item. The dot is used to point to a face. The Architectural tick can be used for referring to multiple parallel edges. The final type of line has no terminator, and is used for pointing at dimension lines or lines of Symmetry.

Leader lines Face and edge

Leader lines can have multiple segments and you can use one annotation to reference multiple faces and edges.

Leader Lines Multiple Leaders

You can reference multiple parallel edges or faces with one leader.

Leader Lines Multiple faces and edges

It is recommended that you draw your leader lines at an angle to the rest of the drawing – i.e. Not parallel to the drawing itself. Increments of 15° are advised.

Leader Lines Angles


Finally, your Instruction text can be centred to the reference line, or it can sit above the reference line. The text should be a least twice the line thickness above the reference line. The text should never touch the reference line itself.

Leader Lines Text

BS ISO 128-22:1999 Technical drawings – General principles of presentation – Part 22: Basic conventions and applications for leader lines and reference lines

8 Responses to “Technical Drawing Standards: Leader Lines.

    6 years ago

    rules of placement of leader lines in drawing

    • Hi Rajat,

      That’s a great idea – and one I will consider writing up in a future post :)


  • Benjamin
    7 years ago

    I’ve been looking for some documentation regarding arrowheads and callouts/leaders. When would it be appropriate to use and Integral symbol for an arrowhead? In the past my thought has been it could be used for something like a face/surface such as the use of the Dot but I haven’t been able to find documentation that would support or refute this idea. What are your thoughts?

    • Hi Benjamin,

      I’m not aware of any use of the Integral type arrowhead in the British Standard, What do you use it to notate?


    • An integral arrowhead means “throughout” effectively. It’s useful for a keynote something like this: new flooring throughout – see finishes schedule.

      • Thanks for clarifying Dan,

        I suspect that items such as flooring wouldn’t be covered in BS8888. Instead we would need to start with Pas 1192 which is that standard for Design documentation in construction.


  • Jack Nardi
    7 years ago

    Excellent distinctions. How about leader to revision clouds? I’m always torn between an arrow to specific issue or just a line to the cloud.

    • Hi Jack,

      Revision clouds aren’t covered in BS8888. I’m guessing that they are more of an Architectural drafting convention?

      Your convention ties into what I’ve seen on Architectural plan sets over the years.

    • Just clouds
    • A triangular ‘Rev’ note, somewhere within the cloud
    • An ‘arrowless’ leader, joining the Rev-note to the cloud
    • No cloud, just a leader from the change to the Rev note
    • No cloud, no leader, no Rev note, revisions are called out using ‘1A’ zones from the Zone border
    • Have I missed any?