How is a carcase (box) assembly made, and which joints are used to build a carcase with four or more joints?
Carcase construction: making a carcase (box) assembly with four or more joints, the carcase joints used (housing, rebate, butt with reinforcement, corner dovetail), fitting a base or back panel, and gluing and cramping the carcase square.
A focused answer to the SQA National 5 Practical Woodworking content on carcase construction, covering carcase joints such as the housing, rebate, reinforced butt and corner dovetail, fitting a base or back panel, and gluing and cramping a box assembly square.
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What this dot point is asking
The SQA wants you to be able to make a carcase (a box) assembly with four or more joints: to know the carcase joints used, how to fit a base or back panel, and how to glue and cramp the box square. A carcase is a three-dimensional box such as a storage box, a small cabinet or a drawer.
What a carcase is
National 5 expects a carcase with four or more joints, proving you can build a rigid box that stays square and holds a base or back panel.
Carcase joints
The main joints used to build a carcase:
- Housing joint - a square groove (housing) cut across one board takes the end of a shelf; supports a shelf and resists it sagging.
- Rebate joint - a step (rebate) cut along an edge so the corner boards overlap; neater and stronger than a plain butt, often used at corners and for back panels.
- Corner dovetail joint - interlocking tails and pins that mechanically lock the corner; the strongest carcase corner.
- Reinforced butt joint - a plain butt strengthened with dowels, glue blocks or nails/screws, used where a simple joint is acceptable.
Fitting a base or back panel
A box usually needs a base or back panel, commonly a sheet of plywood. It is fitted into a rebate or groove cut around the inside of the carcase, then glued (and sometimes pinned). Setting the panel into a rebate or groove keeps it flush, hides the edge and helps square and stiffen the whole box.
Try this
Q1. Name two joints suitable for building a carcase. [2 marks]
- Cue. Any two of: housing, rebate, corner dovetail, reinforced butt.
Q2. State one reason a base panel is set into a groove or rebate. [1 mark]
- Cue. It sits flush and hidden and helps square and stiffen the box (rather than being loose).
Q3. Explain why a dovetail is stronger than a butt joint for a box corner. [2 marks]
- Cue. A dovetail mechanically interlocks (tails and pins) and has a large glue area, so it resists being pulled apart, whereas a butt relies on weak end-grain gluing.
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 build a carcase (box), and describe how a housing joint is made.Show worked answer →
Award 1 mark per named joint (up to 2) and up to 1 for the description, total 3. Suitable carcase joints: housing joint, rebate joint, corner dovetail joint, reinforced (dowelled or blocked) butt joint (1 each for any two). Housing joint: a square groove (the housing) is cut across one piece, usually with a saw to define the sides and a chisel or router to remove the waste; the end of the second piece (a shelf) fits into the groove and is glued (1). Markers reward correctly named carcase joints and an accurate description of the housing.
SQA-style Explain choice3 marksExplain why a corner dovetail joint is a good choice for the corners of a strong box, compared with a plain butt joint.Show worked answer →
Award up to 3 marks for explained reasons. A dovetail joint has interlocking tails and pins that mechanically lock the corner together, so it resists being pulled apart in one direction even before the glue is considered (1). It also has a very large glued surface area, which makes the joint strong and rigid (1). A plain butt joint relies on glue on end grain, which is weak and can be pulled apart easily, so it is much less suitable for a strong box corner (1). Markers reward the mechanical interlock, the large glue area, and the weakness of the butt by comparison.
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