I had a grand idea – I decided I was going to make a HST (half square triangle) quilt.

I knew I wanted to make it a blue and white quilt. I saw a stunning range of fabric (Shibori II by Moda). I knew this would be perfect for what I wanted. I immediately ordered some charm packs in this range with the same number of charm packs of Moda Grunge in Paperwhite. I just knew that they would be stunning together.

With more experience, I would not have bought charm packs as I now realise that there are more economical ways to buy fabric like this. However, the charm packs have the advantage of having a full mix of the fabrics in the range. And I had very little experience of pre-cuts at the time. And the charm pack was gorgeous! Needless to say, the charm packs sat in a drawer while I was finishing my grand opus aka The Beast. (The story of The Beast has been fully covered in my other blogs.)

To construct the HSTs I used the standard method of a pencil line diagonally across the wrong side of the light charm square, place a light and a dark square right sides together, sew 1/4 inch either side of the line and rotary cut along the drawn line.

Then comes the interesting bit – squaring up the HSTs. You can use a standard square ruler with a 45 degree line on it, but there are several tools specially to help with this. I bought 2 (at separate times) – the Clearly Perfect Slotted Trimmer and the BlocLoc ruler. I should make it clear here that I bought both – so I have no allegiance to either company.

I should say that I bought the BlocLoc first. I used it successfully but thought that it was a bit tedious to use – however, I was never the most patient of people. I saw someone using the Clearly Perfect Slotted Trimmer on YouTube and thought that might be easier. When I saw it at a good price I bought this as well.


The Clearly Perfect Slotted Trimmer (shown above) comes in a pack of 2, which covers trimming HSTs of all sizes (at half inch intervals) from 1.5” up to 6.5” square. It is an acrylic triangle with lines across it to indicate where to place the ruler to allow the trimming to take place. There are also slots on each side to allow the dog ears to be removed, which is a big selling point with this ruler.

The BlocLoc (above) is a square acrylic ruler with a milled diagonal groove across the underside. This diagonal groove fits snug against the seam line (when pressed to one side) without slipping over it, allowing the HST to be trimmed on all four sides. The ruler also has the standard markings in inches down to eighths of an inch.

The biggest difference between them is price – the Clearly Perfect Slotted Trimmer comes in at about £35 for the pair and covers 11 sizes – 1.5 inches to 6.5 inches. The BlocLoc costs from £14.60 for the 1.5 inch size to £23.85 for the 6.5 inch size, with each ruler covering a single size, and the finished HST sizes increasing in inches ie 1.5, 2.5 etc. I bought the 4.5 inch size. It should be said that a larger BlocLoc ruler could be used to trim a smaller HST. However, the company do sell sets of combined sizes which carry significant discounts over buying the individual rulers. BlocLoc also make rulers for other shapes, but I have not tried any of those. (Prices are the best I could find at the time of writing.)

The rulers are used in different ways. The Clearly Perfect Slotted ruler is used prior to ironing the HSTs open, by placing the ruler line for the required size on the stitch line, trim the square and trim the dog ears using the slots. One of the selling points is that, in theory, you don’t have to turn the square at all while doing any of the trimming. In practice, it isn’t that simple – I found it awkward to trim, particularly the slots. Getting the rotary cutter into the slots without accidentally moving the ruler involved being a minor contortionist!

Clearly Perfect Slotted Trimmer in place on wrong side of unpressed HST ready for trimming 

The BlocLoc is used after the HST has been ironed open. After ironing the seam allowance to the dark side, you place the milled diagonal line of the ruler against the seam on the right side of the block. The milled line has been engineered so that it will fit snugly up against the seam (you may need to turn it around – it works one way only), allowing the opened out square block to be trimmed on all four sides. Despite the fact that the block needs to be rotated to trim all four sides, I found it very easy to use.

BlocLoc ruler ready for use on the ironed open HST (right side)

I will now make an admission – I trimmed about half of the blocks with the Bloc-Loc and half with the Clearly Perfect. This is obviously not good practice – you should stick to one ruler per project. However, it has allowed a full comparison of the two.

For me, the Clearly Perfect trimmer is quite awkward to use. My stitching lines are not always as straight as they could be, therefore it becomes difficult to decide precisely where the ruler should be placed for trimming. I also found that this ruler is VERY slippery – I know that there are products that can help with this, but it is worth keeping this in mind. Also, I really don’t like the slots for trimming the dog ears – I find it difficult to get the rotary cutter into the slot while keeping the ruler stable on the block.

These are some of the scratches I made on the ruler while trying to trim dog ears!

The BlocLoc ruler I found much easier to use. It feels much sturdier and very well engineered. It does also slip a bit on the fabric, but it seems to slip less. This may be because I found it generally easier to use, so my hold on it was more stable. The major difference is that you either need a rotating cutting mat or a small mat that you can turn around to allow you to trim each side of the square. It also automatically takes off the dog ears.

For me, the main difference between the rulers is accuracy, which became clear when I measured the Clearly Perfect blocks with the BlocLoc. This is not because the templates are different sizes – it is because of the way the rulers are used and the ease of use. If you are like me and have the odd wobbly sewing line, as the Clearly Perfect relies on your sewing line for trimming, where do you put the ruler? Also, even if you have managed to put the ruler on the line in the best place, when you iron the block open you actually magnify by 2 any error that you might have made in the trimming, because you trimmed both halves of the HST exactly the same, which may not be accurate. Also, you might not be ironing quite on the line that you put the ruler on – all of which contribute to inaccuracies.

The possible problems with the BlocLoc are keeping the engineered line up against your seam line and, when you turn your block to trim the other side, to make sure the ruler remains aligned with the sides you have already trimmed. Neither of these are terribly difficult in my opinion.

Are the inaccuracies that you get massive? No they are not. However, I know that I have small inaccuracies at all steps of quilting. Therefore, to me, minimising inaccuracies is important because they add up. Also, if you are making a completely HST quilt, a tiny inaccuracy on each block can soon multiply.

Which one would I choose to use? Assuming I could afford it, I would take the BlocLoc every time. The rulers are the same thickness, so there shouldn’t be any difference in quality – but to me the BlocLoc feels better quality and better engineered. It is easier to use and produces a much more consistent block. Also, if you have any mobility limitations, I would think that the BlocLoc is easier to use.

However, BlocLoc rulers are expensive, particularly if you often make square multiple sizes of HSTs. I don’t know whether more experienced quilters make many different sizes of HSTs, but if you are only likely to make one or two different sizes of HST, I would plump for the BlocLoc.

So I guess you pay your money and take your choice.

This is my experience – I would be interested to hear other opinions.


  1. Christine Galley

    A very interesting review Cheryl. I must admit that I have not used either of those rulers. They both look quite fiddly to use, especially the open slot one, and in my opinion and the price is quite off-putting! I have always used the Quilt in a Day square up ruler and find it so easy to use. You do have to place it on your sewn line and cut your triangle before ironing open, but it’s pretty fail safe. Can be used for HSTs up to 6 ½” and costs less than £10 from Amazon or slightly more expensive from Creative Grids.

    1. Cheryl Davies Post author

      I must admit, I am not sure that your preference in rulers would suit me, as it has a similar problem to the Clearly Perfect ruler, in that you can easily magnify your inaccuracies x2 because you trim the folded block. I must say that I may be a bit obsessive about the accuracy, but I know that small inaccuracies can add up. The BlocLoc is not fiddly to use at all tbh – after doing the comparison I realised that I love it. It is excellent if you have lots of HSTs to trim. However, the prices make me wince!