How to build a simple cat scratching post.

Intro

None of the dimensions are critical.  I wouldn't suggest making the column any taller, or the base any smaller than described.  For cat safety, avoid toxic materials, such as pressure treated wood, and don't leave any sharp points sticking out, such as screws or staples.  If adding dangling strings, use line at least as thick as a shoe lace to reduce temptation to swallow it, if (when) the cats get it loose.  In a multi-cat household, the platform perch may become so popular, you will need to make more than one to reduce fighting over it.

Photo of two cat posts, similar but not identical to the one described.

Materials

Material List
Qty	Size/Type	Material	Use	Notes
8'	2x4	lumber	Column	(not pressure treated)
2'x2'	3/8"	plywood	Base	Exact dimensions aren't critical.
25-30	#10x3"	deck screws	Fastening column	Any type of 2-1/2" or longer flat head screw should work.
100'	1/4"	Sisal rope	Scratching, traction.	3/8" rope would also work. Use natural fiber.  Yes, it takes 100'.
1	tube	Glue, construction adhesive	Rope attachment	Gluing the rope to the column will make it last longer.  Use glue which is non-toxic after curing.
The materials below are only needed if building the optional platform.
18"x18"	1/4"	plywood	Platform	Should be large enough for a sleeping cat, but smaller than the base for stability.
6'	1x2	lumber	Railing	A railing around top edge of platform helps keep snoozing cats from rolling off.  Exact length of 1x2 needed depends on size and shape of platform used.
8-12	#8x1"	deck screws	Fastening railing	Any type of wood screw at least 1/2" longer than the platform thickness should work.
3-4	#8x2"	deck screws	Fastening railing	Any type of small wood screw about 2" long should work.

Tools

• Measuring tape or yardstick.
• Pencil.
• Carpenter's framing square or level.
• Straight edge (at least as long as diagonal of base, yard stick or level  will work).
• C-clamp at least 5" capacity, 7" would be better, can be light duty.
• Saw (7" power circular saw recommended) .
• Drill motor (3/8" variable reversible recommended).
• Drill bits (as required to match screws).
• Screwdriver (as required to match screws, can be power bit for drill motor).
• Staple gun w/1/2" staples (optional, but recommended).
• Router with 1/2" bull nose bit (optional).

Procedure

Cut 2x4

• Measure carefully.  Make certain each cut is straight and square.
• Cut the 2x4 into the following lengths:
• (2 each) 4-1/2"
• (2 each) 5"
• (2 each) cut remainder exactly in half.
• Cut plywood to size if required.

Laminate column

• Carefully align and clamp the two long pieces of 2x4 to form a 4x4.
• Join with three 3" screws at 1/4, 1/2, 3/4 of overall length.

Mark plywood

This step will be easier with more than two hands.

• Mark center of base by drawing lines between diagonally opposite corners.
• Trace 4x4 footprint of column at center of base .
• Use short 2x4 to draw rectangular border 1-1/2" outside of base footprint.
• Repeat same markings on other face of plywood base.  Since the column isn't exactly square, by sure it's footprint lines are oriented the same on both sides of the plywood.
• If adding a platform to the top of the post, then mark platform plywood as above, omitting the 1-1/2" border.

Attach column

• Attach post to center of plywood base with one 3" screw in the center.  Don't tighten this screw completely.  Leave about 1/16" gap between column and base.  (More if end of column isn't flat and square.)
• Clamp one of the 5" 2x4 braces to the column where it meets the plywood base.  
• On edge, so a 5"x1-1/2" side is flat against plywood,
• a 5"x3-1/2" side is flat against column,
• one 1-1/2"x3-1/2" end of brace is flush with one side of column,
• other end of brace is projecting 1-1/2" past other side of column.
• Tighten clamp.
• Attach the brace to the plywood base with two 3" screws about 2" from each end of the brace.  Tighten firmly.
• Repeating the preceding steps, attach the remaining 2x4 braces to the plywood base tight up against the column.  Shorter braces against shorter sides of column.
• While installing the next eight screws, make sure the column remains perpendicular to the plywood base.  If not, the completed scratching post will not be vertical. 
• Attach each brace to the column with two 3" screws.
• Attach each brace to the one it overlaps with one or two 3" screws.
• Add four more 3" screws from the bottom of the base into the column about 3/4" in from each corner of the column's footprint.  Tighten firmly.
• Finally, finish tightening the screw in the center of the base and column.  (Or if you prefer, you can completely remove the center screw.  It is no longer required for strength.  Just don't leave it sticking part way out.)

Wrap column

This step would be easier if done before attaching the column to the base.  But if done in that order, the rope would make it more difficult to tell if the column is exactly perpendicular to the base.

• (Optional)  If router and 1/2" bullnose bit are available, they can be used to radius the corners of the column where the rope will be attached.  Start near the top of the column, and route 1/2" bullnose radius about 2' down four corner edges of column. 
• Attach one end of rope to the side of the column, within an inch of the top end of the column.  This can be done by tying a knot, or by  using several staples.  If using glue, apply some between the end of the rope and the column before tying or stapling, to help prevent the rope from unwinding later. 
• If using glue, apply several inches (but less than a foot) along each side and/or corner of the column ahead of the rope windings.  Fifty feet of rope with cover about a foot of column, so don't apply glue past that point yet if using 50' sections of rope.
• Begin winding the rope tightly around the column, from top towards the bottom.
• Every few turns, tighten the coils against each other by striking or shoving with a piece of scrap wood or similar.  (Something you don't mind getting glue on.)
• Attach tail end of rope to column similar to the way the starting point was attached.
• If using more than one section of rope, overlap sections slightly.  Try to avoid leaving staples exposed where claws could snag on them.  After whacking with the staple gun, drive staples deeper with a small hammer.

Attach platform railing (if adding optional platform)

If building the optional platform on top of the post, consider cutting a large notch in the plywood almost to the center, making it easier for less athletic cats to pull themselves up onto the platform after  clawing their way up the post.  The shape of the notch can be round or rectangular, so long as a fat cat can fit through it.

• Cut 1x2 into lengths 3/4" shorter than each of the outside edges of the platform plywood.
• Attach the railing similar to the column braces, with one end of each railing piece even with the edge of the platform.
• Clamp each piece in place.
• Attach with two or three 1" screws through the plywood into the railing.   Place the screws at least 2" from the end if the railing to avoid splitting or screws hitting each other.
• Where railing ends overlap, fasten together with a 2" screw.

Attach platform to column (if adding optional platform)

Attaching the platform is very similar to the first and last steps in attaching the base.  Just skip the part about the 2x4 braces.  The platform can be installed either before or after winding the rope on the column, which ever seems easier for you.  Installing the platform exactly perpendicular to the column isn't as important as keeping the base perpendicular was.  A slightly slanted platform won't increase the chances of the whole thing tipping over, and the cats certainly won't care.

• If  construction glue is available, put a glob (a teaspoon or two) of glue in the center of the top of the post just before attaching the platform.  After the platform is installed and aligned, the cured glue will provide a shim to fill any uneven gap between the platform and the top of the column. 
• Start with one screw in the center, left a bit loose.
• Add four screws, one near each corner of the column, while keeping the platform perpendicular to the column.
• Start all four screws before final tightening any of them.
• Try to keep the platform perpendicular to the column.  If tightening a screw is pulling the platform out of level, try tightening the diagonally opposite screw first.

Finishing touches

The scratching post can be made more attractive to cats by adding some padding to the platform.  A piece of scrap carpet could be trimmed to fit, or towels folded to fit.  Dangling toys could be attached to the underside or edges of the platform.  A scrap of carpet could be cut to fit the base, with a hole and slit to fit it around the column.  This carpet could then be sprinkled with catnip.