Dimension and extended direction

ben_jiang418

This might be stupid: Let's say I have a 3mm horizontal line. If I use dimension tool and set the length to 6mm, the line is always extended towards the right, eg, the right end always get moved. Is there a way to move the left end instead?

glen_dewsbury

You can fix a point along a line as in this example and it will resize accordingly.
Show constraints in the sketch should make this clear.
Try adding a dimension to each of the 3 lines and note direction of change.
Usually these points are fixed by some other entity.
Just 1 of many ways.
https://cad.onshape.com/documents/51c56c763b52d12b01b6f0cf/w/80d72ccf515beaf60ab9a87a/e/00615a870150f26f26892295

S1mon

It depends on how the line is constrained. You want to use coincident (to something like the origin) or fixed, or some combination of the constraint types to the end you want to stay in place. Then the line will grow in the direction you want.

If any element of the sketch is blue, it's not fully constrained, which makes it difficult and dangerous to predict what will happen.

I would recommend going through the online training.
https://learn.onshape.com/courses/fundamentals-sketching

glen_dewsbury

You can fix a point along a line as in this example and it will resize accordingly.
Show constraints in the sketch should make this clear.
Try adding a dimension to each of the 3 lines and note direction of change.
Usually these points are fixed by some other entity.
Just 1 of many ways.
https://cad.onshape.com/documents/51c56c763b52d12b01b6f0cf/w/80d72ccf515beaf60ab9a87a/e/00615a870150f26f26892295

ben_jiang418

Got it. Thanks, both.