How is a flat-frame assembly made, and which joints are used to build a frame with four or more joints?
Flat-frame construction: making a flat-frame assembly with four or more joints, the frame joints used (corner halving, mortise and tenon, dowel, bridle), and marking out, cutting, fitting, gluing and cramping the frame square.
A focused answer to the SQA National 5 Practical Woodworking content on flat-frame construction, covering frame joints such as the corner halving, mortise and tenon, dowel and bridle joint, and marking out, cutting, fitting, gluing and cramping a frame square.
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What this dot point is asking
The SQA wants you to be able to make a flat-frame assembly with four or more joints: to know the frame joints used, and how to mark out, cut, fit, glue and cramp a frame so it is square and tight. A flat frame is a flat structure such as a picture frame or a door frame.
What a flat frame is
National 5 expects you to assemble a flat frame with four or more joints, which proves you can mark out, cut and fit several joints accurately so the whole frame is square and rigid.
Frame joints
The main joints used to build a flat frame:
- Corner halving joint - each piece is cut away by half its thickness so the two overlap flush; simple and reasonably strong.
- Mortise and tenon joint - a tenon (tongue) cut on one piece fits a mortise (slot) chopped in the other; one of the strongest frame joints.
- Dowel joint - matching holes are drilled in both pieces and glued dowels join them; quick and neat.
- Corner bridle joint - an open mortise (slot through the end) takes a tenon; strong and shows on the face.
Making and assembling the frame
The stages are the same whichever joint is chosen:
- Mark out each joint from the face side and face edge so parts match.
- Cut the joints with the correct saw (tenon saw) and chisel out waste, paring to the lines.
- Dry fit the whole frame to check the joints close and it is square - before any glue.
- Glue the mating surfaces with PVA, assemble, and cramp with sash cramps and softening blocks.
- Check square by measuring the two diagonals (equal diagonals means square) and that the frame is flat, then leave it to set.
Try this
Q1. Name two joints suitable for the corner of a flat frame. [2 marks]
- Cue. Any two of: corner halving, mortise and tenon, dowel, corner bridle.
Q2. State how you check that a glued frame is square. [1 mark]
- Cue. Measure the two diagonals; if they are equal the frame is square (or check with a try square).
Q3. Explain why a dry fit is done before gluing. [2 marks]
- Cue. It checks the joints close and the frame is square while errors can still be corrected; once glued and cramped, the frame cannot easily be adjusted.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA-style Name joints3 marksName three joints that could be used to make the corner of a flat frame, and for one of them describe how it is made.Show worked answer →
Award 1 mark per named joint (up to 2) and up to 1 for a sound description, total 3. Suitable corner frame joints: corner halving joint, mortise and tenon joint, dowel joint, corner bridle joint (1 each for any two). Description, for example the mortise and tenon: a slot (the mortise) is chopped in one piece with a mortise chisel, and a matching tongue (the tenon) is cut on the end of the other piece by sawing the cheeks and shoulders; the tenon fits into the mortise and is glued and cramped (1). Markers reward correctly named frame joints and an accurate description of how one is made.
SQA-style Describe assembly4 marksDescribe the main steps in assembling a flat frame so that it is square and the joints are tight.Show worked answer →
Award 1 mark per valid step, up to 4. Dry fit the frame first to check the joints close and the frame is square before any glue is applied (1). Apply glue (PVA) to the mating surfaces of each joint (1). Cramp the frame together using sash cramps with softening blocks, pulling the joints tight (1). Check the frame is square by measuring the two diagonals (equal diagonals means square) or with a try square, and adjust the cramps until it is, then leave it to set on a flat surface (1). Other valid points: clean off excess glue; check the frame is flat and not twisted. Markers reward dry fit, gluing, cramping and checking for square.
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Sources & how we know this
- National 5 Practical Woodworking course specification — SQA (2025)
- National 5 Practical Woodworking - Course overview — SQA (2026)