Strange. I’ve got an object in the attached file that measures out to a thickness of 7/8" but when I use the dimension tool to dimension it, I get 3/4". I check the length units for the dimension style I’m using and it’s 1/8" – so what could be causing the difference? I wonder if someone could look at the file and at the video I created for it that shows the cross-checking I’ve done to see what might be causing the discrepancy. Tolerances seem to be fine… any help would be appreciated 
Dimension discrepancy.3dm (1.6 MB)
Here is my System Info:
Rhino 7 SR2 2021-1-12 (Rhino 7, 7.2.21012.11001, Git hash:master @ 2f08cf516ffc716c4c4a369abf7625798ef79bca)
License type: Commercial, build 2021-01-12
License details: Cloud Zoo
Windows 10.0.19041 SR0.0 or greater (Physical RAM: 32Gb)
Computer platform: DESKTOP
Standard graphics configuration.
Primary display and OpenGL: NVIDIA Quadro P2000 (NVidia) Memory: 5GB, Driver date: 10-22-2020 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 452.57
> Accelerated graphics device with 4 adapter port(s)
- Windows Main Display attached to adapter port #0
- Secondary monitor attached to adapter port #1
OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
Redraw scene when viewports are exposed: On
Anti-alias mode: 4x
Mip Map Filtering: Linear
Anisotropic Filtering Mode: High
Vendor Name: NVIDIA Corporation
Render version: 4.6
Shading Language: 4.60 NVIDIA
Driver Date: 10-22-2020
Driver Version: 27.21.14.5257
Maximum Texture size: 32768 x 32768
Z-Buffer depth: 24 bits
Maximum Viewport size: 32768 x 32768
Total Video Memory: 5 GB
Rhino plugins that do not ship with Rhino
Rhino plugins that ship with Rhino
C:\Program Files\Rhino WIP\Plug-ins\Commands.rhp “Commands” 7.2.21012.11001
C:\Program Files\Rhino WIP\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino WIP\Plug-ins\RhinoScript.rhp “RhinoScript”
C:\Program Files\Rhino WIP\Plug-ins\RPC.rhp “RPC”
C:\Program Files\Rhino WIP\Plug-ins\RhinoRenderCycles.rhp “Rhino Render” 7.2.21012.11001
C:\Program Files\Rhino WIP\Plug-ins\RhinoRender.rhp “Legacy Rhino Render”
C:\Program Files\Rhino WIP\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 7.2.21012.11001
C:\Program Files\Rhino WIP\Plug-ins\rdk_ui.rhp “Renderer Development Kit UI”
C:\Program Files\Rhino WIP\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino WIP\Plug-ins\RhinoCycles.rhp “RhinoCycles” 7.2.21012.11001
C:\Program Files\Rhino WIP\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 7.2.21012.11001
C:\Program Files\Rhino WIP\Plug-ins\3dxrhino.rhp “3Dconnexion 3D Mouse”
C:\Program Files\Rhino WIP\Plug-ins\Displacement.rhp “Displacement”
