> ## Documentation Index
> Fetch the complete documentation index at: https://help.yournewdoor.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Door Fundamentals
> The first lesson every sales rep must complete — slab vs. prehung, size shorthand, interior vs. exterior, and the four qualifying questions.
# Door Fundamentals
Complete this page before moving to Door Anatomy. Every term and concept here comes up in every customer conversation and every quote.
Before quoting any door, a rep must understand the two basic product categories and how door sizes are communicated in the industry. Getting this wrong leads to quoting the wrong product and missing critical fit details.
## Slab vs. Prehung
This is the first and most important question to answer on every job. Most replacement jobs are prehung.
A **slab** is the door panel only. It does not include the frame, hinges, threshold, or any jamb components.
**When to use slab:**
* The existing frame is in good condition and structurally sound
* The customer only needs a new door panel
* The frame is still square and the existing hinge locations match the new slab
**What you must capture for a slab order:**
* Exact panel width, height, and thickness
* Existing hinge backset and count
* Lock bore location and backset
* Whether the frame is wood, fiberglass composite, or metal
Always verify that the existing frame is square before recommending a slab replacement. An out-of-square frame will cause fit and operation problems regardless of slab quality.
A **prehung unit** includes the slab already mounted in its own frame assembly, typically with hinges, lock prep, and sometimes threshold and casing.
**When to use prehung:**
* The existing frame is damaged, rotted, or out of square
* The installation is new construction
* The customer wants a full system replacement
* The hinge or bore locations on the existing frame do not match available slab prep
**What you must capture for a prehung order:**
* Rough opening width and height
* Jamb depth (must match wall thickness)
* Handing and swing direction
* Threshold type and sill conditions
* Casing or brickmould requirements
Prehung units are sized by the rough opening or unit size, not the slab alone. Always confirm which size convention you are using when entering the order.
A rep cannot build an accurate quote until they know whether the customer needs a slab or a prehung unit. This single question changes measurements, hardware options, pricing, and install assumptions.
## How Door Sizes Work
Door sizes use a four-digit shorthand that is standard across the industry. The first two digits are the width in feet and inches, the last two are the height.
| Shorthand | Width | Height | Common Use |
| ------------------------ | ----- | ------ | ----------------------- |
| 2068 | 2'0" | 6'8" | Interior bedroom/closet |
| 2468 | 2'4" | 6'8" | Interior narrow passage |
| 2668 | 2'6" | 6'8" | Interior standard |
| 2868 | 2'8" | 6'8" | Interior standard |
| 3068 | 3'0" | 6'8" | Exterior entry standard |
| 3080 | 3'0" | 8'0" | Exterior tall entry |
| 6068 | 6'0" | 6'8" | Double door entry |
| 6080 | 6'0" | 8'0" | Double door tall entry |
When a customer says "I need a 3068 door," always confirm whether they mean the **slab size** or the **full unit callout**. For prehung units, the unit is typically 2" wider and 1" taller than the slab to account for the frame. Do not assume.
## Interior vs. Exterior
Exterior and interior doors have fundamentally different construction and performance requirements. Always confirm which application the customer needs before recommending a product.
### Exterior Doors
* Weather-rated construction required
* Threshold and weatherstripping included
* Higher core density for insulation and security
* Glass units must be insulated (IGU)
* Brickmould or casing may be required
* Finish must be rated for sun and moisture exposure
### Interior Doors
* No weather resistance required
* No threshold standard
* Lower core density acceptable
* Glass can be single-pane or decorative
* Casing is standard trim detail, not weather seal
* Paint-grade or stain-grade finishes both common
## New Construction vs. Replacement
There is no existing door unit. The rough opening is being framed to size and the door unit goes in as part of the build. The rep needs the rough opening dimensions from the builder's plans and must confirm framing specs. No existing frame condition to assess.
An existing door unit is being removed and replaced. The rep must account for the existing opening dimensions, the frame condition (square, rotted, damaged?), trim reuse, and whether the new unit will cover any existing damage or gaps at the rough opening edge.
## The Four Qualifying Questions
Every customer conversation should answer these four questions before any measurement discussion begins.
Determines the entire scope of the order and what measurements you need.
Sets performance requirements, glass specs, threshold needs, and material options.
Determines whether you are working from framing plans or field measurements.
Changes the total configuration width, active panel sizing, and handing reference point.
Print this page or save it to your phone. Run through these four questions at the top of every intake call before you open a quote.