I tried to use the measurement tool to measure the height between the
two left arrows.  There is a measurable point at the top, but no
measurable point at the bottom, nor is there a line to grab.

I isolated the relevant code, and the above "bug" disappears: the bottom
measurable point is now available.  Here is that code:

//

include <BOSL2/std.scad>

eps = 0.01;
slop = 0.2;
$fa = 3;
$fs = 0.2;
inches = 25.4;

down(2)
left(15) fwd(15)
    cube([30, 30, 2]);
// monitor mount
difference() {
    cylinder(h = 16, d = 20);
    cylinder(h = 16, d = 3.8);
    up(19)
        sphere(d = 18);
    cube(20);
    }

And here is the original code, where the "bug" exists.  I am puzzled at
the difference.

//

include <BOSL2/std.scad>

eps = 0.01;
slop = 0.2;
$fa = 3;
$fs = 0.2;
inches = 25.4;

le = 2.00 * inches;        // length (X)
dt = 5.18 * inches;        // depth top (Y)
db = 5.33 * inches;        // depth bottom (Y)
ht = 1.45 * inches;        // height (Z)
uc = 0.22 * inches;        // under cut (Y)
th = 2;

// near side
cube([le, th, ht]);
// near undercut
down(th)
    cube([le, uc + th, th]);
// top
up(ht)
    cube([le, db + 2*th, th]);
// far side
back(th + db)
    cube([le, th, ht]);
// far undercut
down(th) back(th + db - uc)
    cube([le, uc + th, th]);

// monitor mount
right(le/2)
back(db/2)
up(ht)
difference() {
    cylinder(h = 16, d = 20);
    cylinder(h = 16, d = 3.8);
    up(19)
        sphere(d = 18);
    cube(20);
    }

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Thank you, Michael.  I use 3D Tool for measurement, too.  I was trying to point out an anomaly.  Perhaps I should create an Issue out of it, but I wanted some feedback first.

On 5/18/2026 7:29 AM, Michael Möller wrote:
May or may not help you, I did an STL of both examples and used a different program (3D Tool, Free) to measure.

[image.png]
I am running plain vanilla OpenSCAD V2021.0.1 and the BOSL is june'23

On Sat, 16 May 2026 at 17:01, Jon Bondy via Discuss <discuss@lists.openscad.orgmailto:discuss@lists.openscad.org> wrote:

I tried to use the measurement tool to measure the height between the two left arrows.  There is a measurable point at the top, but no measurable point at the bottom, nor is there a line to grab.

[cid:part2.K0GXWCwx.6pZBoJfB@jonbondy.com]

I isolated the relevant code, and the above "bug" disappears: the bottom measurable point is now available.  Here is that code:

//

include <BOSL2/std.scad>

eps = 0.01;
slop = 0.2;
$fa = 3;
$fs = 0.2;
inches = 25.4;

down(2)
left(15) fwd(15)
cube([30, 30, 2]);
// monitor mount
difference() {
cylinder(h = 16, d = 20);
cylinder(h = 16, d = 3.8);
up(19)
sphere(d = 18);
cube(20);
}

And here is the original code, where the "bug" exists.  I am puzzled at the difference.

//

include <BOSL2/std.scad>

eps = 0.01;
slop = 0.2;
$fa = 3;
$fs = 0.2;
inches = 25.4;

le = 2.00 * inches;        // length (X)
dt = 5.18 * inches;        // depth top (Y)
db = 5.33 * inches;        // depth bottom (Y)
ht = 1.45 * inches;        // height (Z)
uc = 0.22 * inches;        // under cut (Y)
th = 2;

// near side
cube([le, th, ht]);
// near undercut
down(th)
cube([le, uc + th, th]);
// top
up(ht)
cube([le, db + 2*th, th]);
// far side
back(th + db)
cube([le, th, ht]);
// far undercut
down(th) back(th + db - uc)
cube([le, uc + th, th]);

// monitor mount
right(le/2)
back(db/2)
up(ht)
difference() {
cylinder(h = 16, d = 20);
cylinder(h = 16, d = 3.8);
up(19)
sphere(d = 18);
cube(20);
}

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I was able to measure that distance.  I get 8.20595.  I haven't used the
measurement stuff much, but it seemed to just work: render, click
measure icon, point at one end, see diamond, click, point at the other
end, see diamond, click.

Yes.  In my "production" code (bottom in my original post), here, the diamond appears at the top but not at the bottom; in the trimmed down example code (top in my original post), the bottom diamond appears.  My point was that 1) the diamond is not appearing in what seems like an obvious location, and B) the two sets of code seem too similar for them to behave differently as to the diamonds.

On 5/18/2026 11:40 AM, Jordan Brown wrote:
I was able to measure that distance.  I get 8.20595.  I haven't used the measurement stuff much, but it seemed to just work: render, click measure icon, point at one end, see diamond, click, point at the other end, see diamond, click.