Using edge distance and or the pinch setting in soft selection could help. or you could temporarily detach the polygons and then weld them back together. Whats the problem specifically?.

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Basically, i'm using edit mesh on a plane to create a large bumpy piece of ground, and I want to be able to freely move vertices up and down with soft selection over a relatively large area without having to worry about crossing over the edges of the area of the plane i want to edit.
In short, i want to prevent the vertices at the edges of that area from moving, which would prevent me from crossing over the edge.
Using edge distance would be difficult, since i still want to edit a large area.
still, detaching might work, i should have thought of that , thnx

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!!!
Under "soft selection" "paint" lets you paint in selection value you want. in this case paint zero on sections you don't want modified.

When you toggle "lock soft selection" you can select a big area, then paint out what you don't want modified.

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