How to modify heights of model created by a sketch in the X-Y pane?

[adi.barda]

Hello,
I have created a simple sketch with some constraints on the X-Y pane and then pad it.
Now that I have a 3D model out of my sketch, I would like to put some more constraints so that the rear and front heights of the model will not be the same size (see attachment)

The model after padding the sketch

freecad_question1.jpg (36.32 KiB) Viewed 512 times

And, here is the sketch that was padded:

The sketch that was padded

freecad_question1_sketch.jpg (145.95 KiB) Viewed 512 times

It's a beginner question but I spent a lot of hours before submitting that question
Thanks you,
Adi Barda

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.6706 (Git)
Build type: Release
Branch: releases/FreeCAD-0-16
Hash: f86a4e411ff7848dea98d7242f43b7774bee8fa0
Python version: 2.7.8
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

[bejant]

Hi Adi and welcome! Select one of the 20 mm faces, click the Create Sketch tool, and Sketcher a triangle. Use the Link To External Geometry tool to create edges from Pad so you can constrain vertices of the triangle onto them:

20170417a.png (8.1 KiB) Viewed 502 times

Then Pocket "Through All"

20170417a-016-adi.barda.fcstd

(17.54 KiB) Downloaded 15 times

OS: Ubuntu 16.04.2 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.16.6707 (Git)
Build type: None
Branch: releases/FreeCAD-0-16
Hash: 5465bc47c95db45e0be85dc0e2872419efadce0f
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17